day1/handout.tex
author Santosh G. Vattam <vattam.santosh@gmail.com>
Fri, 06 Nov 2009 18:39:56 +0530
changeset 291 ec70a2048871
parent 92 d9c31aacd835
permissions -rw-r--r--
Updated cheatsheet for session 2.
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\documentclass[12pt]{article}
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\title{Python Workshop\\Problems and Exercises}
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\author{Asokan Pichai\\Prabhu Ramachandran}
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\begin{document}
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\maketitle
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\section{Python}
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\subsection{Getting started}
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   \begin{verbatim}
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>>> print 'Hello Python' 
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>>> print 3124 * 126789
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>>> 1786 % 12
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>>> 3124 * 126789
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>>> a = 3124 * 126789
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>>> big = 12345678901234567890 ** 3
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>>> verybig = big * big * big * big 
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>>> 12345**6, 12345**67, 12345**678
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>>> s = 'Hello '
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>>> p = 'World'
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>>> s + p 
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>>> s * 12 
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>>> s * s
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>>> s + p * 12, (s + p)* 12
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>>> s * 12 + p * 12
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>>> 12 * s 
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\end{verbatim}
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\newpage
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\begin{verbatim}
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>>> 17/2
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>>> 17/2.0
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>>> 17.0/2
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>>> 17.0/8.5
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>>> int(17/2.0)
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>>> float(17/2)
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>>> str(17/2.0)
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>>> round( 7.5 )
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\end{verbatim}
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\subsection{Mini exercises}
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\begin{itemize}
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  \item Round a float to the nearest integer, using \texttt{int()}?
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  \item What does this do?  \\\texttt{round(amount * 10) /10.0 }
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  \item How to round a number to the nearest  5 paise?
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    \begin{description}
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      \item[Remember] 17.23 $\rightarrow$ 17.25,\\ while 17.22 $\rightarrow$ 17.20
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    \end{description}
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  \item How to round a number to the nearest 20 paise?
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\end{itemize}
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\begin{verbatim}
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    amount = 12.68
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    denom = 0.05
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    nCoins = round(amount/denom)
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    rAmount = nCoins * denom
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\end{verbatim}
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\subsection{Dynamic typing}
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\begin{verbatim}
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a = 1
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a = 1.1
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a = "Now I am a string!"
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\end{verbatim}
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\subsection{Comments}
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\begin{verbatim}
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a = 1  # In-line comments
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# Comment in a line to itself.
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a = "# This is not a comment!"
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  \end{verbatim}
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\section{Data types}
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\subsection{Numbers}
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  \begin{verbatim}
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>>> a = 1 # Int.
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>>> l = 1000000L # Long
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>>> e = 1.01325e5 # float
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>>> f = 3.14159 # float
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>>> c = 1+1j # Complex!
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>>> print f*c/a
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(3.14159+3.14159j)
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>>> print c.real, c.imag
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1.0 1.0
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>>> abs(c)
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1.4142135623730951
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>>> abs( 8 - 9.5 )
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1.5
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  \end{verbatim}
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\subsection{Boolean}
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  \begin{verbatim}
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>>> t = True
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>>> f = not t
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False
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>>> f or t
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True
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>>> f and t
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False
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>>>  NOT True
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\ldots ???
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>>>  not TRUE
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\ldots ???
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\end{verbatim}
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\subsection{Relational and logical operators}
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  \begin{verbatim}
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>>> a, b, c = -1, 0, 1
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>>> a == b
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False
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>>> a <= b 
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True
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>>> a + b != c
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True
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>>> a < b < c
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True
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>>> c >= a + b
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True
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  \end{verbatim}
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\subsection{Strings}
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  \begin{verbatim}
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s = 'this is a string'
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s = 'This one has "quotes" inside!'
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s = "I have 'single-quotes' inside!"
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l = "A string spanning many lines\
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one more line\
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yet another"
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t = """A triple quoted string does
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not need to be escaped at the end and 
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"can have nested quotes" etc."""
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  \end{verbatim}
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  \begin{verbatim}
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>>> w = "hello"    
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>>> print w[0] + w[2] + w[-1]
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hlo
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>>> len(w) # guess what
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5
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>>> s = u'Unicode strings!'
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>>> # Raw strings (note the leading 'r')
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... r_s = r'A string $\alpha \nu$'
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  \end{verbatim}
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  \begin{verbatim}
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>>> w[0] = 'H' # Can't do that!
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Traceback (most recent call last):
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  File "<stdin>", line 1, in ?
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TypeError: object does not support item assignment
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  \end{verbatim}
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  \subsection{IPython}
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  \begin{verbatim}
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In [1]: a = 'hello world'
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In [2]: a.startswith('hell')
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Out[2]: True
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In [3]: a.endswith('ld')
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Out[3]: True
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In [4]: a.upper()
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Out[4]: 'HELLO WORLD'
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In [5]: a.upper().lower()
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Out[5]: 'hello world'
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In [6]: a.split()
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Out[6]: ['hello', 'world']
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In [7]: ''.join(['a', 'b', 'c'])
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Out[7]: 'abc'
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In [8] 'd' in ''.join( 'a', 'b', 'c')
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Out[8]: False
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a.split( 'o' )}
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???
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'x'.join( a.split( 'o' ) )
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???
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In [11]: x, y = 1, 1.2
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In [12]: 'x is %s, y is %s' %(x, y)
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Out[12]: 'x is 1, y is 1.234'
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'x is \%d, y is \%f' \%(x, y)
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???
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'x is \%3d, y is \%4.2f' \%(x, y)
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??? 
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  \end{verbatim}
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\subsection{A classic problem}
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    How to interchange values of two variables? Please note that the type of either variable is unknown and it is not necessary that both be of the same type even!
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\subsection{Basic conditional flow}
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  \begin{verbatim}
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In [21]: a = 7
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In [22]: b = 8
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In [23]: if a > b:
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   ....:    print 'Hello'
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   ....: else:
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   ....:     print 'World'
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   ....:
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   ....:
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World
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  \end{verbatim}
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\subsection{\texttt{If...elif...else} example}
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\begin{verbatim}
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x = int(raw_input("Enter an integer:"))
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if x < 0:
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     print 'Be positive!'
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elif x == 0:
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     print 'Zero'
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elif x == 1:
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     print 'Single'
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else:
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     print 'More'
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\end{verbatim}
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\subsection{Basic looping}
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  \begin{verbatim}
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# Fibonacci series:
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# the sum of two elements
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# defines the next
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a, b = 0, 1
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while b < 10:
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    print b,
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    a, b = b, a + b
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\end{verbatim}
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\section{Problem set 1}
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All the problems can be solved using \texttt{if} and \texttt{while} 
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\begin{description}
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  \item[1.1] Write a program that displays all three digit numbers that are equal to the sum of the cubes of their digits. That is, print numbers $abc$ that have the property $abc = a^3 + b^3 + c^3$\\
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These are called $Armstrong$ numbers.
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\item[1.2 Collatz sequence]
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\begin{enumerate}
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  \item Start with an arbitrary (positive) integer. 
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  \item If the number is even, divide by 2; if the number is odd multiply by 3 and add 1.
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  \item Repeat the procedure with the new number.
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  \item There is a cycle of 4, 2, 1 at which the procedure loops.
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\end{enumerate}
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    Write a program that accepts the starting value and prints out the Collatz sequence.
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   239
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\item[1.3]
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  Write a program that prints the following pyramid on the screen. 
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  \begin{verbatim}
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1
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2  2
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3  3  3
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4  4  4  4
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  \end{verbatim}
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The number of lines must be obtained from the user as input.\\
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When can your code fail?
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\end{description}
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\subsection{Functions: examples}
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  \begin{verbatim}
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def signum( r ):
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    """returns 0 if r is zero
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    -1 if r is negative
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    +1 if r is positive"""
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    if r < 0:
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        return -1
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    elif r > 0:
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        return 1
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    else:
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        return 0
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def pad( n, size ): 
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    """pads integer n with spaces
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    into a string of length size
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    """
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    SPACE = ' '
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    s = str( n )
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    padSize = size - len( s )
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    return padSize * SPACE + s
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  \end{verbatim}
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What about \%3d?
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\subsection  {What does this function do?}
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  \begin{verbatim}
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def what( n ):
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    if n < 0: n = -n
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    while n > 0:
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        if n % 2 == 1:
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            return False
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Shantanu <shantanu@fossee.in>
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   283
        n /= 10
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    return True
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  \end{verbatim}
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   286
\newpage
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\subsection{What does this function do?}
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\begin{verbatim}
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def what( n ):
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    i = 1    
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    while i * i < n:
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        i += 1
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    return i * i == n, i
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  \end{verbatim}
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\subsection{What does this function do?}
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  \begin{verbatim}
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def what( n, x ):
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    z = 1.0
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    if n < 0:
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        x = 1.0 / x
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        n = -n
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    while n > 0:
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        if n % 2 == 1:
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            z *= x
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        n /= 2
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        x *= x
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    return z
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  \end{verbatim}
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\section{Problem set 2}
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  The focus is on writing functions and calling them.
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\begin{description}
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  \item[2.1] Write a function to return the gcd of two numbers.
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  \item[2.2 Primitive Pythagorean Triads] A pythagorean triad $(a,b,c)$ has the property $a^2 + b^2 = c^2$.\\By primitive we mean triads that do not `depend' on others. For example, (4,3,5) is a variant of (3,4,5) and hence is not primitive. And (10,24,26) is easily derived from (5,12,13) and should not be displayed by our program. \\
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Write a program to print primitive pythagorean triads. The program should generate all triads with a, b values in the range 0---100
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\item[2.3] Write a program that generates a list of all four digit numbers that have all their digits even and are perfect squares.\\For example, the output should include 6400 but not 8100 (one digit is odd) or 4248 (not a perfect square).
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\item[2.4 Aliquot] The aliquot of a number is defined as: the sum of the \emph{proper} divisors of the number. For example, the aliquot(12) = 1 + 2 + 3 + 4 + 6 = 16.\\
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  Write a function that returns the aliquot number of a given number. 
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\item[2.5 Amicable pairs] A pair of numbers (a, b) is said to be \emph{amicable} if the aliquot number of a is b and the aliquot number of b is a.\\
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  Example: \texttt{220, 284}\\
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  Write a program that prints all five digit amicable pairs.
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Shantanu <shantanu@fossee.in>
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\end{description}
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\section{Lists}
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parents:
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\subsection{List creation and indexing}
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Shantanu <shantanu@fossee.in>
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   328
\begin{verbatim}
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>>> a = [] # An empty list.
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>>> a = [1, 2, 3, 4] # More useful.
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   331
>>> len(a) 
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4
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>>> a[0] + a[1] + a[2] + a[-1]
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   334
10
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Shantanu <shantanu@fossee.in>
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diff changeset
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\end{verbatim}
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diff changeset
   336
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\begin{verbatim}
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diff changeset
   338
>>> a[1:3] # A slice.
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diff changeset
   339
[2, 3]
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diff changeset
   340
>>> a[1:-1]
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diff changeset
   341
[2, 3, 4]
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diff changeset
   342
>>> a[1:] == a[1:-1]
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   343
False  
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   344
\end{verbatim}
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diff changeset
   345
Explain last result
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diff changeset
   346
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\newpage
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   348
\subsection{List: more slices}
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Shantanu <shantanu@fossee.in>
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diff changeset
   349
\begin{verbatim}
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Shantanu <shantanu@fossee.in>
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diff changeset
   350
>>> a[0:-1:2] # Notice the step!
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Shantanu <shantanu@fossee.in>
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diff changeset
   351
[1, 3]
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Shantanu <shantanu@fossee.in>
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diff changeset
   352
>>> a[::2]
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diff changeset
   353
[1, 3]
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diff changeset
   354
>>> a[-1::-1]
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Shantanu <shantanu@fossee.in>
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diff changeset
   355
\end{verbatim}
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diff changeset
   356
What do you think the last one will do?\\
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Shantanu <shantanu@fossee.in>
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   357
\emph{Note: Strings also use same indexing and slicing.}
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diff changeset
   358
  \subsection{List: examples}
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diff changeset
   359
\begin{verbatim}
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diff changeset
   360
>>> a = [1, 2, 3, 4]
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diff changeset
   361
>>> a[:2]
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diff changeset
   362
[1, 3]
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diff changeset
   363
>>> a[0:-1:2]
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parents:
diff changeset
   364
[1, 3]
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diff changeset
   365
\end{verbatim}
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parents:
diff changeset
   366
\emph{Lists are mutable (unlike strings)}
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diff changeset
   367
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diff changeset
   368
\begin{verbatim}
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parents:
diff changeset
   369
>>> a[1] = 20
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diff changeset
   370
>>> a
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Shantanu <shantanu@fossee.in>
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diff changeset
   371
[1, 20, 3, 4]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   372
\end{verbatim}
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parents:
diff changeset
   373
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   374
  \subsection{Lists are mutable and heterogenous}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   375
\begin{verbatim}
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parents:
diff changeset
   376
>>> a = ['spam', 'eggs', 100, 1234]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   377
>>> a[2] = a[2] + 23
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   378
>>> a
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parents:
diff changeset
   379
['spam', 'eggs', 123, 1234]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   380
>>> a[0:2] = [1, 12] # Replace items
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   381
>>> a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   382
[1, 12, 123, 1234]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   383
>>> a[0:2] = [] # Remove items
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   384
>>> a.append( 12345 )
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   385
>>> a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   386
[123, 1234, 12345]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   387
\end{verbatim}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   388
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   389
  \subsection{List methods}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   390
\begin{verbatim}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   391
>>> a = ['spam', 'eggs', 1, 12]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   392
>>> a.reverse() # in situ
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   393
>>> a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   394
[12, 1, 'eggs', 'spam']
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   395
>>> a.append(['x', 1]) 
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   396
>>> a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   397
[12, 1, 'eggs', 'spam', ['x', 1]]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   398
>>> a.extend([1,2]) # Extend the list.
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   399
>>> a.remove( 'spam' )
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   400
>>> a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   401
[12, 1, 'eggs', ['x', 1], 1, 2]
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   402
\end{verbatim}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   403
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   404
  \subsection{List containership}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   405
  \begin{verbatim}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   406
>>> a = ['cat', 'dog', 'rat', 'croc']
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   407
>>> 'dog' in a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   408
True
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   409
>>> 'snake' in a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   410
False
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   411
>>> 'snake' not in a
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   412
True
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   413
>>> 'ell' in 'hello world'
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   414
True
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   415
  \end{verbatim}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   416
  \subsection{Tuples: immutable}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   417
\begin{verbatim}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   418
>>> t = (0, 1, 2)
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   419
>>> print t[0], t[1], t[2], t[-1] 
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   420
0 1 2 2
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   421
>>> t[0] = 1
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   422
Traceback (most recent call last):
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   423
  File "<stdin>", line 1, in ?
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   424
TypeError: object does not support item assignment
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   425
\end{verbatim}  
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   426
    Multiple return values are actually a tuple.\\
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   427
    Exchange is tuple (un)packing
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   428
  \subsection{\texttt{range()} function}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   429
  \begin{verbatim}
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Shantanu <shantanu@fossee.in>
parents:
diff changeset
   430
>>> range(7)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   431
[0, 1, 2, 3, 4, 5, 6]
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   432
>>> range( 3, 9)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   433
[3, 4, 5, 6, 7, 8]
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   434
>>> range( 4, 17, 3)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   435
[4, 7, 10, 13, 16]
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   436
>>> range( 5, 1, -1)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   437
[5, 4, 3, 2]
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   438
>>> range( 8, 12, -1)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   439
[]
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   440
  \end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   441
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   442
  \subsection{\texttt{for\ldots range(\ldots)} idiom}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   443
  \begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   444
In [83]: for i in range(5):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   445
   ....:     print i, i * i
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   446
   ....:     
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   447
   ....:     
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   448
0 0
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   449
1 1
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   450
2 4
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   451
3 9
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   452
4 16
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   453
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   454
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   455
  \subsection{\texttt{for}: the list companion}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   456
  
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   457
  \begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   458
In [84]: a = ['a', 'b', 'c']
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   459
In [85]: for x in a:
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   460
   ....:    print x, chr( ord(x) + 10 )
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   461
   ....:
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   462
a  k
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   463
b  l
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   464
c  m
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   465
  \end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   466
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   467
  \subsection{\texttt{for}: the list companion}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   468
  \begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   469
In [89]: for p, ch in enumerate( a ):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   470
   ....:     print p, ch
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   471
   ....:     
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   472
   ....:     
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   473
0 a
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   474
1 b
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   475
2 c
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   476
  \end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   477
Try: \texttt{print enumerate(a)}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   478
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   479
\section{Problem set 3}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   480
  As you can guess, idea is to use \texttt{for}!
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   481
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   482
\begin{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   483
  \item[3.1] Which of the earlier problems is simpler when we use \texttt{for} instead of \texttt{while}? 
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   484
  \item[3.2] Given an empty chessboard and one Bishop placed in any square, say (r, c), generate the list of all squares the Bishop could move to.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   485
  \item[3.3] Given two real numbers \texttt{a, b}, and an integer \texttt{N}, write a
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   486
  function named \texttt{linspace( a, b, N)} that returns an ordered list
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   487
  of \texttt{N} points starting with \texttt{a} and ending in \texttt{b} and
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   488
  equally spaced.\\
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   489
  For example, \texttt{linspace(0, 5, 11)}, should return, \\
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   490
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   491
[ 0.0 ,  0.5,  1.0 ,  1.5,  2.0 ,  2.5,  
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   492
  3.0 ,  3.5,  4.0 ,  4.5,  5.0 ]
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   493
\end{verbatim}
92
d9c31aacd835 Made little changes to handout.tex.
Santosh G. Vattam <vattam.santosh@gmail.com>
parents: 70
diff changeset
   494
  \item[3.4] Use the \texttt{linspace} function and generate a list of N tuples of the form\\
62
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   495
\texttt{[($x_1$,f($x_1$)),($x_2$,f($x_2$)),\ldots,($x_N$,f($x_N$))]}\\for the following functions,
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   496
\begin{itemize}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   497
  \item \texttt{f(x) = sin(x)}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   498
  \item \texttt{f(x) = sin(x) + sin(10*x)}.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   499
\end{itemize}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   500
92
d9c31aacd835 Made little changes to handout.tex.
Santosh G. Vattam <vattam.santosh@gmail.com>
parents: 70
diff changeset
   501
\item[3.5] Using the tuples generated earlier, determine the intervals where the roots of the functions lie.
62
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   502
\end{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   503
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   504
\section{IO}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   505
  \subsection{Simple tokenizing and parsing}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   506
  \begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   507
s = """The quick brown fox jumped
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   508
       over the lazy dog"""
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   509
for word in s.split():
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   510
    print word.capitalize()
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   511
  \end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   512
92
d9c31aacd835 Made little changes to handout.tex.
Santosh G. Vattam <vattam.santosh@gmail.com>
parents: 70
diff changeset
   513
\section{Problem Set 4}
62
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   514
  \begin{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   515
    \item[4.1] Given a string like, ``1, 3-7, 12, 15, 18-21'', produce the list\\
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   516
      \texttt{[1,3,4,5,6,7,12,15,18,19,20,21]}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   517
\end{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   518
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   519
  \subsection{File handling}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   520
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   521
>>> f = open('/path/to/file_name')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   522
>>> data = f.read() # Read entire file.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   523
>>> line = f.readline() # Read one line.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   524
>>> f.close() # close the file.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   525
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   526
Writing files
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   527
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   528
>>> f = open('/path/to/file_name', 'w')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   529
>>> f.write('hello world\n')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   530
>>> f.close()
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   531
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   532
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   533
    \subsection{File and \texttt{for}}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   534
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   535
>>> f = open('/path/to/file_name')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   536
>>> for line in f:
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   537
...     print line
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   538
...
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   539
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   540
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   541
  \begin{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   542
    \item[4.2] The given file has lakhs of records in the form:
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   543
    \texttt{RGN;ID;NAME;MARK1;\ldots;MARK5;TOTAL;PFW}.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   544
    Some entries may be empty.  Read the data from this file and print the
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   545
    name of the student with the maximum total marks.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   546
  \item[4.3] For the same data file compute the average marks in different
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   547
    subjects, the student with the maximum mark in each subject and also
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   548
    the standard deviation of the marks.  Do this efficiently.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   549
\end{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   550
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   551
\section{Modules}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   552
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   553
>>> sqrt(2)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   554
Traceback (most recent call last):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   555
  File "<stdin>", line 1, in <module>
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   556
NameError: name 'sqrt' is not defined
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   557
>>> import math        
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   558
>>> math.sqrt(2)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   559
1.4142135623730951
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   560
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   561
>>> from math import sqrt
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   562
>>> from math import *
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   563
>>> from os.path import exists
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   564
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   565
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   566
  \subsection{Modules: example}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   567
  \begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   568
# --- arith.py ---
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   569
def gcd(a, b):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   570
    if a%b == 0: return b
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   571
    return gcd(b, a%b)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   572
def lcm(a, b):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   573
    return a*b/gcd(a, b)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   574
# ------------------
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   575
>>> import arith
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   576
>>> arith.gcd(26, 65)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   577
13
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   578
>>> arith.lcm(26, 65)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   579
130
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   580
  \end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   581
\section{Problem set 5}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   582
  \begin{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   583
    \item[5.1] Put all the functions you have written so far as part of the problems
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   584
  into one module called \texttt{iitb.py} and use this module from IPython.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   585
  \end{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   586
\newpage
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   587
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   588
\section{Data Structures}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   589
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   590
   \subsection{Dictonary}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   591
   \begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   592
>>>d = { 'Hitchhiker\'s guide' : 42, 'Terminator' : 'I\'ll be back'}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   593
>>>d['Terminator']
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   594
"I'll be back"
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   595
   \end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   596
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   597
\subsection{Problem Set 6.1}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   598
\begin{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   599
\item[6.1.1] You are given date strings of the form ``29, Jul 2009'', or ``4 January 2008''. In other words a number a string and another number, with a comma sometimes separating the items.Write a function that takes such a string and returns a tuple (yyyy, mm, dd) where all three elements are ints.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   600
\item[6.1.2] Count word frequencies in a file.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   601
\item[6.1.3] Find the most used Python keywords in your Python code (import keyword).
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   602
\end{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   603
\subsection{Set}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   604
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   605
>>> f10 = set([1,2,3,5,8])
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   606
>>> p10 = set([2,3,5,7])
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   607
>>> f10|p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   608
set([1, 2, 3, 5, 7, 8])
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   609
>>> f10&p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   610
set([2, 3, 5])
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   611
>>> f10-p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   612
set([8, 1])
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   613
>>> p10-f10, f10^p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   614
set([7]), set([1, 7, 8])
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   615
>>> set([2,3]) < p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   616
True
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   617
>>> set([2,3]) <= p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   618
True
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   619
>>> 2 in p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   620
True
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   621
>>> 4 in p10
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   622
False
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   623
>>> len(f10)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   624
5
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   625
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   626
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   627
\subsection{Problem Set 6.2}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   628
\begin{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   629
  \item[6.2.1] Given a dictionary of the names of students and their marks, identify how many duplicate marks are there? and what are these?
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   630
  \item[6.2.2] Given a string of the form ``4-7, 9, 12, 15'' find the numbers missing in this list for a given range.
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   631
\end{description}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   632
\subsection{Fuctions: default arguments}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   633
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   634
def ask_ok(prompt, complaint='Yes or no!'):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   635
    while True:
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   636
        ok = raw_input(prompt)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   637
        if ok in ('y', 'ye', 'yes'): 
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   638
            return True
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   639
        if ok in ('n', 'no', 'nop',
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   640
                  'nope'): 
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   641
            return False
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   642
        print complaint
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   643
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   644
ask_ok('?')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   645
ask_ok('?', '[Y/N]')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   646
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   647
\newpage
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   648
\subsection{Fuctions: keyword arguments}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   649
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   650
def ask_ok(prompt, complaint='Yes or no!'):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   651
    while True:
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   652
        ok = raw_input(prompt)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   653
        if ok in ('y', 'ye', 'yes'): 
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   654
            return True
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   655
        if ok in ('n', 'no', 'nop',
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   656
                  'nope'): 
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   657
            return False
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   658
        print complaint
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   659
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   660
ask_ok(prompt='?')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   661
ask_ok(prompt='?', complaint='[y/n]')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   662
ask_ok(complaint='[y/n]', prompt='?')
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   663
\end{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   664
\subsection{List Comprehensions}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   665
Lets say we want to squares of all the numbers from 1 to 100
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   666
\begin{verbatim}
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   667
squares = []
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   668
for i in range(1, 100):
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   669
    squares.append(i * i)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   670
# list comprehension
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   671
squares = [i*i for i in range(1, 100)
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   672
           if i % 10 in [1, 2, 5, 7]]
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   673
\end{verbatim}
70
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   674
\newpage
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   675
\section{Further Reference:}
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   676
\begin{itemize}
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   677
  \item Most referred and trusted material for learning \emph{Python} language is available at docs.python.org/tutorial/
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   678
  \item ``may be one of the thinnest programming language books on my shelf, but it's also one of the best.'' -- \emph{Slashdot, AccordianGuy, September 8, 2004}- available at diveintopython.org/
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   679
  \item How to Think Like a Computer Scientist: Learning with Python available at http://www.openbookproject.net/thinkcs/python/english/ \\
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   680
    ``The concepts covered here apply to all programming languages and to problem solving in general.'' -- \emph{Guido van Rossum, creator of Python}
b138c4ac68e6 Added reference part in handouts for first day.
Shantanu <shantanu@fossee.in>
parents: 62
diff changeset
   681
\end{itemize}
62
12bd6784d213 Forgot to add files, doing them now.
Shantanu <shantanu@fossee.in>
parents:
diff changeset
   682
\end{document}