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Roshansahurk
Roshansahurk

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String Methods

What are Strings?

  • Strings are the data structures which store a sequence of characters.

  • Strings are immutable i.e. they cannot be changed.

  • Ex: "Hello"

  • "Hello" is a string of characters with characters 'h', 'e', 'l', 'l', and 'o' in it.

  • A string can be initialised by single quotes and double quotes. It throws an array if used in combinations of single quotes and double quotes.

  • Initialise a string.

    >>> s = 'abcde'
    >>> s   #Prints the output
    'abcde'
    
  • The indexing on a string starts with 0 from the start and -1 from the end.

  • Accessing a particular index in a string.

    >>> s = 'Hello'
    >>> s[2]
    l
    >>> s[-4]
    e
    
  • Concatenation in a string.

    >>> a = "Python"
    >>> b = "3.7"
    >>> a + " " + b
    "Python 3.7"
    
  • Slicing in a string is done with the help of square brackets.

  • s[start:stop:step]

    >>> s = 'Pythonist'
    >>> s[2:4]
    th
    

Helper Functions in strings

  • string.capitalize()

    Returns a copy of a string with the first letter capitalised.

    >>> s.capitalize()
    'Abcde'
    
    
  • string.lower()

    Return a copy of a string with all the characters in lowercase.

    >>> a = 'Hello WORLD'
    >>> a.lower()
    hello world
    
  • string.upper()

    Return a copy of a string with all the characters in lowercase.

    >>> a.upper()
    HELLO WORLD   
    
  • string.split()

    Returns a list with the space-separated elements.

    >>> a.split()
    ["Hello", "World"]
    
  • string.join()

    Returns a string by joining the entire set of characters in a list or a tuple.

    >>> l1 = ['H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd']
    >>> ''.join(l1)
    'Hello World'
    
  • string.swapcase()

    Returns a copy of string but with lowercase letters to uppercase and vice versa.

    >>> a = 'Python'
    >>> a.swapcase()
    'pYTHON'
    
  • string.casefold()

    Return a copy of a string with all the characters in lowercase. It is the same as the string.lower()

    >>> a = 'Hello WORLD'
    >>> a.casefold()
    hello world
    
  • string.center(width, fill_char)

    Returns a copy of the string in the centre with added spaces to the right and left. It takes space as a fill character if nothing is given.

    >>> s = 'HELLO'
    >>> s.center(30, '-')
    '------------HELLO-------------'
    
    
  • string.count(string)

    Returns an integer value stating the number of occurrences of a string in a string.

    >>> s = 'HELLO'
    >>> s.count('L')    
    2
    
  • string.endswith(string)

    Returns True if the string end with the specified string.

    >>> s = 'Python'
    >>> s.endswith("on")
    True
    
  • string.index(string)

    Returns the index of the first occurrence in a string.

    >>> s = 'Hello World'
    >>> s.index('o')
    4
    
  • string.isalnum()

    Returns True if all characters in the string are alphanumeric.

    >>> s = 'AabcD123'
    >>> s.isalnum()
    True    
    
  • string.isalpha()

    Returns True if all characters in the string are in the alphabet.

    >>> s = 'abcd'
    >>> s.isalpha()
    True
    
  • string.isdecimal()

    Returns True if all characters in the string are decimals.

    >>> s = '1234'
    >>> s.isdecimal()
    True
    
  • string.isdigit()

    Returns True if all characters in the string are digits.

    >>> s = '1234'
    >>> s.isdecimal()
    True    
    
  • string.islower()

    Returns True if all characters in the string are lowercase.

    >>> s = 'abcd'
    >>> s.islower()
    True    
    
  • string.isupper()

    Returns True if all characters in the string are uppercase.

    >>> s = 'ABCD'
    >>> s.isupper()
    True    
    

References

  • To know more about the helper functions in a string, click on the below link.

    String Methods

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