--- a/strings.org Wed Apr 21 18:43:36 2010 +0530
+++ b/strings.org Wed Apr 21 20:09:16 2010 +0530
@@ -24,11 +24,13 @@
look at how to do elementary string manipulation, and simple input
and output operations.
- As, we have seen in previous tutorials, anything enclosed within
- quotes is a string. For example -
+ In Python anything enclosed within quotes is a string. Lets get
+ started by starting ipython interpreter. We shall create some
+ string variables by:
a = 'This is a string'
print a
+ type(a) shows it is 'str'
b = "This too!"
print b
@@ -44,11 +46,12 @@
These are special type of strings, called docstrings, which shall
be discussed along with functions.
- Like lists, which we already saw, string elements can be accessed
- with their indexes. The indexing here, also, begins from 0.
+ Like lists and arrays, which we have already seen, string elements
+ can also be accessed with their indexes. The indexing here, also,
+ begins from 0.
- print a[0]
- print a[5]
+ print a[0] gives us 'T'
+ print a[5] gives us 'i' which is 6th character.
To access the last element, we can use -1 as the index!
print a[-1]
@@ -60,7 +63,9 @@
len(a)
Python's strings support the operations + and *
+ + concatenates two strings.
a + b
+ and * is used for replicating a string for given number of times.
a * 4
What do you think would happen when you do a * a?
It's obviously an error since, it doesn't make any logical sense.
@@ -93,20 +98,21 @@
Python also has a 'join' function, which does the opposite of what
split does.
' '.join(alist) will return the original string a.
+ This function takes list of elements(in our case alist) to be joined.
'-'.join(alist) will return a string with the spaces in the string
'a' replaced with hyphens.
At times we want our output or message in a particular
format with variables embedded, something like printf in C. For
those situations python provides a provision. First lets create some
- variables
+ variables say
* formatting - printf style *
In []: x, y = 1, 1.234
In []: print 'x is %s, y is %s' %(x, y)
Out[]: 'x is 1, y is 1.234'
Here %s means string, you can also try %d or %f for integer and
- float values.
+ float values respectively.
* formatting - printf style *
@@ -151,11 +157,11 @@
Before we wind up, a couple of miscellaneous things.
As you may have already noticed, Python is a dynamically typed
language, that is you don't have to specify the type of a variable
- when using a new one. You don't have to do anything special, to use
+ when using a new one. You don't have to do anything special, to 'reuse'
a variable that was of int type as a float or string.
- a = 1
- a = 1.1
+ a = 1 here a is integer
+ a = 1.1 now a float
a = "Now I am a string!"
Comments in Python start with a pound or hash sign. Anything after
@@ -166,7 +172,7 @@
a = "# not a comment"
we come to the end of this tutorial on strings introduction of Data types in
- Python. In this tutorial we have learnt what are supported data types,
- supported operations and performing simple IO operations in Python.
+ Python. In this tutorial we have learnt what are supported operations and
+ performing simple IO operations in Python.
*** Notes