Data structures in python continued.. (strings) .. [P-2]

[Humble]

Python has different data structures like :

Strings
lists
tuples
Dictionaries

Lets start with strings:

1) Strings can be represented either in double quotes or in single quotes..

>>>> ex = "I am a string"
>>> type(ex)
<type 'str'>
>>> ex = 'I am a string'
>>> type(ex)
<type 'str'>
>>> ex
'I am a string'
>>> 
>>> 



2) Strings can be indexed:

>
>>> for i in ex:
...     print i
... 
I
 
a
m
 
a
 
s
t
r
i
n
g
>>> 

>>> ex[0]
'I'
>>> ex[1]
' '
>>> ex[2]
'a'
>>> ex[3]
'm'
>>> 




3) Strings can be concatenated

>>>> "Hi "+ex
'Hi I am a string'
>>>


4)  some important methods/functions  of "string"  :


upper()
lower()
split()
strip()
join()
replace()
....

Examples on upper() and lower()

>>>> ex
'I am a String'
>>> 

>>> ex.upper()
'I AM A STRING'
>>> ex.lower()
'i am a string'

>>>



|  split(...)
|      S.split([sep [,maxsplit]]) -> list of strings
|
|      Return a list of the words in the string S, using sep as the
|      delimiter string.  If maxsplit is given, at most maxsplit
|      splits are done. If sep is not specified or is None, any
|      whitespace string is a separator and empty strings are removed
|      from the result.
|


You can specify the delimiter , if so, it will be splitted based on that 'delimiter', if not, it will be splitted based on "whitspace"..

see, below example:

>>>> ex= 'I am good: how are you'
>>> ex
'I am good: how are you'
>>> ex.split(':')
['I am good', ' how are you']
>>> ex
'I am good: how are you'
>>> ex.split()
['I', 'am', 'good:', 'how', 'are', 'you']
>>> 




 |
|  strip(...)
|      S.strip([chars]) -> string or unicode
|
|      Return a copy of the string S with leading and trailing
|      whitespace removed.
|      If chars is given and not None, remove characters in chars instead.
|      If chars is unicode, S will be converted to unicode before stripping

>
>>> ex = '     I am good: and how are you  '
>>> ex
'     I am good: and how are you  '
>>> ex.strip()
'I am good: and how are you'
>>> ex
'     I am good: and how are you  '

>>> ex= 'malayalam'
>>> ex.strip('m')
'alayala'
>>> ex.strip('a')
'malayalam'
>>> 



When using strips please think that its going to strip only from start and end, and it returns a copy.. The original string is intact..



 |  replace(...)
|      S.replace(old, new[, count]) -> string
|
|      Return a copy of string S with all occurrences of substring
|      old replaced by new.  If the optional argument count is
|      given, only the first count occurrences are replaced.

>>>> ex
'malayalam'
>>> ex.replace('a','j',3)
'mjljyjlam'
>>> ex.replace('al','jk')
'mjkayjkam'
>>> ex.replace('al','')
'mayam'
>>> 



 |  join(...)
|      S.join(iterable) -> string
|
|      Return a string which is the concatenation of the strings in the
|      iterable.  The separator between elements is S.

>>>> ex
'malayalam'
>>> ':'.join(ex)
'm:a:l:a:y:a:l:a:m'

>>> "Hi".join(ex)
'mHiaHilHiaHiyHiaHilHiaHim'
>>> 




It continues... how-ever some more examples

index example

>>>> ex
'malayalam'
>>> ex.index('y')
4
>>> ex[4]
'y'
>>>



count example:

>>>> ex.count('a')
4
>>> ex.count('m')
2
>>> ex.count('l')
2
>>> 


length of the string

>>>> ex
'malayalam'
>>> len(ex)
9
>>> ex="Hi hope it helps"
>>> len(ex)
16
>>> 




Strings can be used with format specifiers..

>>>> print ("hi " + "%s" + " dude") %(ex)
hi hope it helps dude





How-ever strings are immutable:

>>>> ex[1]
'o'
>>> ex[2]
'p'
>>> ex
'hope it helps'
>>> ex[2]='k'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'str' object does not support item assignment
>>>




you can convert any other data types to strings by 'str'

>>>> x
1
>>> type(x)
<type 'int'>
>>> str(x)
'1'
>>> type(str(x))
<type 'str'>




Shoot your queries about python strings here.....

[Humble]

Some more slicing examples:

>>> str= "humble"
>>> str[::-2]
'ebu'
>>> str[::2]
'hml'
>>> str[1:2]
'u'
>>> str[1::]
'umble'
>>> str[::3]
'hb'
>>> str[:3]
'hum'
>>> 

[Author]

Posts