String Funtion and Method

Function :

A function is a block of code to carry out a specific task, will contain its own scope and is called by name. All functions may contain zero(no) arguments or more than one arguments. On exit, a function can or can not return one or more values.

  • Function is block of code that is also called by its name. (independent) 
  • The function can have different parameters or may not have any at all. If any data (parameters) are passed, they are passed explicitly. 
  • It may or may not return any data. 
  • Function does not deal with Class and its instance concept.

    
    def functionName( arg1, arg2,….):
       …….
       # Function_body
       ……..


Method

A method in python is somewhat similar to a function, except it is associated with object/classes. Methods in python are very similar to functions except for two major differences.

  • Method is called by its name, but it is associated to an object (dependent).
  • A method is implicitly passed the object on which it is invoked. 
  • It may or may not return any data.
  • A method can operate on the data (instance variables) that is contained by the corresponding class

    class ClassName:
       def method_name():
          …………..
          # Method_body
          ………………

Built-in String Methods

Python includes the following built-in methods to manipulate strings −

  • capitalize() - Capitalizes first letter of string.

Example - 


    s="apkZube"
    print(s.capitalize())  #Apkzube

output of above example  :


    Apkzube
  • count() - The count() method returns the number of occurrences of substring sub in the range [start, end]. Optional arguments start and end are interpreted as in slice notation.

Syntax : 

str.count(sub, start = 0,end = len(string))

  • sub − This is the substring to be searched. 
  • start − Search starts from this index. First character starts from 0 index. By default search starts from 0 index. 
  • end − Search ends from this index. First character starts from 0 index. By default search ends at the last index. 

    
    s="I Love Python Tutorial"
    print(s.count('o'))  #3
    print(s.count('o',5))  #2
    print(s.count('t'))  #2
    print(s.count('t',2,9))  #0

output of above example  :


  3
  2
  2
  0
  • index() - The index() method determines if the string str occurs in string or in a substring of string, if the starting index beg and ending index end are given. This method is same as find(), but raises an exception if sub is not found.

syntax : str.index(str, beg ,end ) 

  • str − This specifies the string to be searched.
  • beg − This is the starting index, by default its 0. 
  • end − This is the ending index, by default its equal to the length of the string.

    s="I Love Python Tutorial"
    print(s.index('i'))
    print(s.index('i',2))
    print(s.index('Love'))
    print(s.index('Love',7))
    print(s.index('i',0,10))

output of above example  :


    19
    0
    19
    2
    Traceback (most recent call last):
      File "main.py", line 16, in 
        print(s.index('Love',7)    
    ValueError: substring not found
  • find() - The find() method determines if the string str occurs in string, or in a substring of string if the starting index beg and ending index end are given.

str.find(str, beg, end)

  • str − This specifies the string to be searched. 
  • beg − This is the starting index, by default its 0. 
  • end − This is the ending index, by default its equal to the lenght of the string.



    s="I Love Python Tutorial"
    print(s.find('I'))
    print(s.find('I',2))
    print(s.find('Love'))
    print(s.find('t',2,10))

output of above example  :


0
-1
2
9
  • isalpha() - The isalpha() method checks whether the string consists of alphabetic characters only.

syntax - str.isalpha()




    s="I Love Python 3 Tutorial" 
    print(s.isalpha())    
    s="Python" # No space & digit in this string   
    print(s.isalpha())

output of above example  :


False
True
  • isalnum() - The isalnum() method checks whether the string consists of alphanumeric characters.

 str.isalnum()




    s="I Love Python 3 Tutorial" 
    print(s.isalnum())
    
    s="Python" # No space  
    print(s.isalnum())

output of above example  :


False
True
  • isdigit() - The method isdigit() checks whether the string consists of digits only.
Syntax - str.isdigit()



    s="I Love Python 3 Tutorial" 

    print(s.isdigit())
    s="123" # Only digit in this string    
    print(s.isdigit())

output of above example  :


False
True
  •  islower()  - The islower() method checks whether all the case-based characters (letters) of the string are lowercase.

example :


    s="I Love Python 3 Tutorial"

    print(s.islower())
    p="python"
    print(p.islower())

output of above example  :


False
True
  • isnumeric() - The isnumeric() method checks whether the string consists of only numeric characters. This method is present only on unicode objects.

Note − Unlike Python 2, all strings are represented in Unicode in Python 3. Given below is an example illustrating it.

Example : 


    str = "apkzube97"  

    print (str.isnumeric())
    str = "10121997"
    print (str.isnumeric())

output of above example  :


False
True
  • isspace() - The isspace() method checks whether the string consists of whitespace

Example : 


    str = " "  

    print (str.isspace())
    str = "apkzube"
    print (str.isspace())

output of above example  :


True
False
  • istitle() - The istitle() method checks whether all the case-based characters in the string following non-casebased letters are uppercase and all other case-based characters are lowercase.

Explanation:


    s1='I Love Python Tutorial'

    print(s1.istitle())
    s2='I love python 3'
    print(s2.istitle())

output of above example  :


True
False
  • len() - The len() method returns the length of the string.

Example - 


    s1='I Love Python Tutorial'

    print(len(s1))
    s2='I love python 3'
    print(len(s2))

output of above example  :


22
15
  • lower() - The method lower() returns a copy of the string in which all case-based characters have been lowercased.

Example - 


    s1='I Love Python Tutorial'

    print(s1.lower())
    s2='I love python 3'
    print(s2.lower())

output of above example  :


    i love python tutorial
    i love python 3
  • upper() - The upper() method returns a copy of the string in which all case-based characters have been uppercased

Example - 


    s1='I Love Python Tutorial'

    print(s1.upper())
    s2='I love python 3'
    print(s2.upper())

output of above example  :


    I LOVE PYTHON TUTORIAL
    I LOVE PYTHON 3
  • max() - The max() method returns the max alphabetical character from the string str.
Example - 

    s1='I Love Python Tutorial'

    print(max(s1))
    s2='apkzube'
    print(max(s2))

output of above example :


y
z
  • min() - The min() method returns the min alphabetical character from the string str.

Example - 


    s1='PythonTutorial'

    print(min(s1))
    s2='apkzube'
    print(min(s2))

output of above example  :


P
a
  • lstrip() - The lstrip() method returns a copy of the string in which all chars have been stripped from the beginning of the string (default whitespace characters).
  • rstrip() - The rstrip() method returns a copy of the string in which all chars have been stripped from the end of the string (default whitespace characters).

str.lstrip([chars])

str.rstrip([chars])
Example -


    s1=' I Love Python Tutorial '

    print(s1.lstrip())
    s2='###ApkZube###'
    print(s2.lstrip('#'))

output of above example  :


    I Love Python Tutorial
    ApkZube###
    ###ApkZube
  • replace - The replace() method returns a copy of the string in which the occurrences of old have been replaced with new, optionally restricting the number of replacements to max.

str.replace(old, new,[max])

Exmple - 

  • old − This is old substring to be replaced. 
  • new − This is new substring, which would replace old substring. 
  • max − If this optional argument max is given, only the first count occurrences are replaced. 

    s1='I Love Python Tutorial, I Love ApkZube, I Love Coding'
    print(s1.replace('Love','Like'))
    print(s1.replace('I','He',2))

output of above example  :


    I Like Python Tutorial, I Like ApkZube, I Like Coding
    He Love Python Tutorial, He Love ApkZube, I Love Coding
  • split() - The split() method returns a list of all the words in the string, using str as the separator (splits on all whitespace if left unspecified), optionally limiting the number of splits to num.

str.split(str="", num = string.count(str)).

Example - 

  • str − This is any delimeter, by default it is space. 
  • num − this is number of lines to be made 

    s1='I Love Python,Java,Android,PHP,JavaScript'
    print(s1.split(','))
    print(s1.split(',',2)) #total 3 element in list

output of above example  :


    ['I Love Python', 'Java', 'Android', 'PHP', 'JavaScript']
    ['I Love Python', 'Java', 'Android,PHP,JavaScript']
  • swapcase() - The swapcase() method returns a copy of the string in which all the case-based characters have had their case swapped.

Example - 


    s1='I Love Python,Java,Android,PHP,JavaScript'
    print(s1.swapcase())

output of above example  :


    i lOVE pYTHON,jAVA,aNDROID,php,jAVAsCRIPT