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%Tutorial slides on Python.
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% Author: FOSSEE
% Copyright (c) 2009, FOSSEE, IIT Bombay
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\usepackage{listings}
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% Title page
\title[Basic Python]{Python language: Basics}
\author[FOSSEE Team] {The FOSSEE Group}
\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}
\date[] {13 February, 2010\\Day 2, Session 3}
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%% Delete this, if you do not want the table of contents to pop up at
%% the beginning of each subsection:
\AtBeginSubsection[]
{
\begin{frame}<beamer>
\frametitle{Outline}
\tableofcontents[currentsection,currentsubsection]
\end{frame}
}
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{
\begin{frame}<beamer>
\frametitle{Outline}
\tableofcontents[currentsection,currentsubsection]
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% DOCUMENT STARTS
\begin{document}
\begin{frame}
\titlepage
\end{frame}
\begin{frame}
\frametitle{Outline}
\tableofcontents
% You might wish to add the option [pausesections]
\end{frame}
\section{Data types}
\begin{frame}
\frametitle{Primitive Data types}
\begin{itemize}
\item Numbers: float, int, complex
\item Strings
\item Booleans
\end{itemize}
\end{frame}
\subsection{Numbers}
\begin{frame}[fragile]
\frametitle{Numbers}
\begin{itemize}
\item \kwrd{int}\\ whole number, no matter what the size!
\begin{lstlisting}
In []: a = 13
In []: b = 99999999999999999999
\end{lstlisting}
\item \kwrd{float}
\begin{lstlisting}
In []: p = 3.141592
\end{lstlisting}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Complex numbers}
\begin{lstlisting}
In []: c = 3+4j
In []: abs(c)
Out[]: 5.0
In []: c.imag
Out[]: 4.0
In []: c.real
Out[]: 3.0
\end{lstlisting}
\end{frame}
\subsection{Booleans}
\begin{frame}[fragile]
\frametitle{Booleans}
\begin{lstlisting}
In []: t = True
In []: f = not t
In []: f or t
Out[]: True
In []: f and t
Out[]: False
\end{lstlisting}
\inctime{5}
\end{frame}
\begin{frame}[fragile]
\frametitle{( ) for precedence}
\begin{lstlisting}
In []: a = False
In []: b = True
In []: c = True
In []: (a and b) or c
Out[]: True
In []: a and (b or c)
Out[]: False
\end{lstlisting}
\inctime{5}
\end{frame}
\subsection{Strings}
\begin{frame}[fragile]
\frametitle{Strings}
Strings were introduced previously, let us now look at them in a little more detail.
\begin{lstlisting}
In []: w = "hello"
In []: print w[0] + w[2] + w[-1]
Out[]: hlo
In []: len(w)
Out[]: 5
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Strings \ldots}
\emphbar{Strings are immutable}
\begin{lstlisting}
In []: w[0] = 'H'
\end{lstlisting}
\pause
\begin{lstlisting}
--------------------------------------------
TypeError Traceback (most recent call last)
/<ipython console> in <module>()
TypeError: 'str' object does not
support item assignment
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{String methods}
\begin{lstlisting}
In []: a = 'Hello World'
In []: a.startswith('Hell')
Out[]: True
In []: a.endswith('ld')
Out[]: True
In []: a.upper()
Out[]: 'HELLO WORLD'
In []: a.lower()
Out[]: 'hello world'
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{A bit about IPython}
Recall, we showed a few features of IPython, here is one more:
\begin{itemize}
\item IPython provides better help
\item object.function?
\begin{lstlisting}
In []: a = 'Hello World'
In []: a.lower?
\end{lstlisting}
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Still with strings}
\begin{itemize}
\item We saw split() yesterday
\item join() is the opposite of split()
\end{itemize}
\begin{lstlisting}
In []: ''.join(['a', 'b', 'c'])
Out[]: 'abc'
In []: ', '.join(['a', 'b', 'c'])
Out[]: 'a, b, c'
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{String formatting}
\begin{lstlisting}
In []: x, y = 1, 1.234
In []: 'x is %s, y is %s' %(x, y)
Out[]: 'x is 1, y is 1.234'
\end{lstlisting}
\begin{itemize}
\item \emph{\%d}, \emph{\%f} etc. available
\end{itemize}
\emphbar{\url{http://docs.python.org/library/stdtypes.html}}
\inctime{10}
\end{frame}
\section{Operators}
\begin{frame}[fragile]
\frametitle{Arithmetic operators}
\small
\begin{lstlisting}
In []: 1786 % 12
Out[]: 10
In []: 45 % 2
Out[]: 1
In []: 864675 % 10
Out[]: 5
In []: 3124 * 126789
Out[]: 396088836
In []: big = 1234567891234567890 ** 3
In []: verybig = big * big * big * big
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Arithmetic operators}
\begin{lstlisting}
In []: 17 / 2
Out[]: 8
In []: 17 / 2.0
Out[]: 8.5
In []: 17.0 / 2
Out[]: 8.5
In []: 17.0 / 8.5
Out[]: 2.0
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Arithmetic operators}
\begin{lstlisting}
In []: a = 7546
In []: a += 1
In []: a
Out[]: 7547
In []: a -= 5
In []: a
In []: a *= 2
In []: a /= 5
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{String operations}
\begin{lstlisting}
In []: s = 'Hello'
In []: p = 'World'
In []: s + p
Out[]: 'HelloWorld'
In []: s * 4
Out[]: 'HelloHelloHelloHello'
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{String operations \ldots}
\begin{lstlisting}
In []: s * s
\end{lstlisting}
\pause
\begin{lstlisting}
--------------------------------------------
TypeError Traceback (most recent call last)
/<ipython console> in <module>()
TypeError: can`t multiply sequence by
non-int of type `str`
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Relational and logical operators}
\begin{lstlisting}
In []: p, z, n = 1, 0, -1
In []: p == n
Out[]: False
In []: p >= n
Out[]: True
In []: n < z < p
Out[]: True
In []: p + n != z
Out[]: False
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Built-ins}
\begin{lstlisting}
In []: int(17 / 2.0)
Out[]: 8
In []: float(17 / 2)
Out[]: 8.0
In []: str(17 / 2.0)
Out[]: '8.5'
In []: round( 7.5 )
Out[]: 8.0
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Odds and ends}
\begin{itemize}
\item Case sensitive
\item Dynamically typed $\Rightarrow$ need not specify a type
\begin{lstlisting}
In []: a = 1
In []: a = 1.1
In []: a = "Now I am a string!"
\end{lstlisting}
\item Comments:
\begin{lstlisting}
In []: a = 1 # In-line comments
In []: # A comment line.
In []: a = "# Not a comment!"
\end{lstlisting}
\end{itemize}
\inctime{15}
\end{frame}
\section{Simple IO}
\begin{frame}[fragile]
\frametitle{Simple IO: Console Input}
\small
\begin{itemize}
\item raw\_input() waits for user input.
\begin{lstlisting}
In []: a = raw_input()
5
In []: a
Out[]: '5'
In []: a = raw_input('Enter a value: ')
Enter a value: 5
\end{lstlisting}
\item Prompt string is optional.
\item All keystrokes are Strings!
\item \texttt{int()} converts string to int.
\end{itemize}
\end{frame}
\begin{frame}[fragile]
\frametitle{Simple IO: Console output}
\begin{itemize}
\item \typ{print} is straight forward
\item Put the following code snippet in a file \typ{hello1.py}
\end{itemize}
\begin{lstlisting}
print "Hello"
print "World"
In []: %run -i hello1.py
Hello
World
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{Simple IO: Console output \ldots}
Put the following code snippet in a file \typ{hello2.py}
\begin{lstlisting}
print "Hello",
print "World"
In []: %run -i hello2.py
Hello World
\end{lstlisting}
\emphbar{Note the distinction between \typ{print x} and \typ{print x,}}
\end{frame}
\section{Control flow}
\begin{frame}
\frametitle{Control flow constructs}
\begin{itemize}
\item \kwrd{if/elif/else}: branching
\item \kwrd{C if X else D}: Ternary conditional operator
\item \kwrd{while}: looping
\item \kwrd{for}: iterating
\item \kwrd{break, continue}: modify loop
\item \kwrd{pass}: syntactic filler
\end{itemize}
\end{frame}
\subsection{Basic Conditional flow}
\begin{frame}[fragile]
\frametitle{\typ{If...elif...else} example}
Type the following code in an editor \& save as \alert{ladder.py}
\small
\begin{lstlisting}
x = int(raw_input("Enter an integer:"))
if x < 0:
print 'Be positive!'
elif x == 0:
print 'Zero'
elif x == 1:
print 'Single'
else:
print 'More'
\end{lstlisting}
\inctime{10}
\end{frame}
\begin{frame}[fragile]
\frametitle{Ternary conditional operator}
\begin{lstlisting}
...
a = raw_input('Enter number(Q to quit):')
num = int(a) if a != 'Q' else 0
...
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{What did we learn?}
\begin{itemize}
\item Data types: int, float, complex, boolean, string
\item Operators: +, -, *, /, \%, **, +=, -=, *=, /=, >, <, <=, >=, ==, !=, a < b < c
\item Simple IO: \kwrd{raw\_input} and \kwrd{print}
\item Conditional structures: \kwrd{if/elif/else},\\ \kwrd{C if X else D}
\end{itemize}
\end{frame}
\end{document}
%% Questions for Quiz %%
%% ------------------ %%
\begin{frame}
\frametitle{\incqno }
What is the largest integer value that can be represented natively by Python?
\end{frame}
\begin{frame}
\frametitle{\incqno }
What is the result of 17.0 / 2?
\end{frame}
\begin{frame}
\frametitle{\incqno }
Which of the following is not a type in Python?
\begin{enumerate}
\item int
\item float
\item char
\item string
\end{enumerate}
\end{frame}
\begin{frame}
\frametitle{\incqno }
How do you create a complex number with real part 2 and imaginary part
0.5.
\end{frame}
\begin{frame}
\frametitle{\incqno }
What is the difference between \kwrd{print} \emph{x} and \kwrd{print} \emph{x,} ?
\end{frame}
\begin{frame}
\frametitle{\incqno }
What does '*' * 40 produce?
\end{frame}
\begin{frame}[fragile]
\frametitle{\incqno }
What is the output of:
\begin{lstlisting}
In []: ', '.join(['a', 'b', 'c'])
\end{lstlisting}
\end{frame}
\begin{frame}[fragile]
\frametitle{\incqno}
\begin{lstlisting}
In []: 47 % 3
\end{lstlisting}
What is the output?
\end{frame}