String Methods in Python

• lower()

  Converts all uppercase characters in a string into lowercase.
  

  my_str="Hello World"
  print(my_str.lower()) # hello world
  print(my_str) # Hello World
  

• islower()

  Checks if all characters in the string are lowercase.
  

  str = 'Hello World'
  print(str.islower()) # False
  
  str = 'hello world'
  print(str.islower()) # True
  

• casefold()

  Returns a string where all the characters are lower case.
  

  my_str="HeLLo World"
  print(my_str.casefold()) # hello world
  

• upper()

  Converts all lowercase characters in a string into uppercase.
  

  my_str="Hello World"
  print(my_str.upper()) # HELLO WORLD
  print(my_str) # Hello World
  

• isupper()

  Checks if all characters in the string are uppercase.
  

  str = 'Hello World'
  print(str.isupper()) # False
  
  str = 'HELLO'
  print(str.isupper()) # True
  

• title()

  Convert string to title case
  

  my_str="hello world"
  print(my_str.title()) # Hello World
  

• istitle()

  Returns “True” if the string is a title cased string.
  

  str = 'Hello World'
  print(str.istitle()) # True
  
  str = 'hello world'
  print(str.istitle()) # False
  

• capitalize()

  Convert the first character of a string to capital (uppercase) letter.
  

  my_str="hello world"
  print(my_str.capitalize()) # Hello world
  

• swapcase()

  Swap the cases of all characters in a string.
  

  my_str="Hello World"
  print(my_str.swapcase()) # hELLO wORLD
  

• center()

  Pad the string with the specified character upto specified length.
  

  my_str="Hello World"
  print(my_str.center(16,'a')) # aaHello Worldaaa
  print(my_str.center(20,'a')) # aaaaHello Worldaaaaa
  

• count()

  Returns the number of occurrences of a substring in the string.
  

  my_str="Hello World Hello Hello"
  print(my_str.count("Hello")) # 3
  print(my_str.count('l')) # 7
  

• encode()

  Encodes strings with the specified encoded scheme.
  In case of failure, it raises a UnicodeDecodeError exception.
  

  my_str="Hello World"
  # change encoding to utf-8
  print(my_str.encode()) # b'Hello World'
  

• endswith()

  Returns “True” if a string ends with the given suffix.
  

  my_str="Hello World"
  print(my_str.endswith("World")) # True
  

• expandtabs()

  Specifies the amount of space to be substituted with the “\t” symbol in the string. Default tabsize is 8.
  

  str = 'Hello\tWorld'
  print(str.expandtabs()) # Hello   World
  print(str.expandtabs(20)) # Hello               World
  

• find()

  Returns the lowest index of the substring if it is found.
  

  str = 'Hello World'
  print(str.find("World")) # 6
  print(str.find("Galaxy")) # -1
  

• index()

  Returns the position of the first occurrence of a substring in a string.
  If substring doesn't exist inside the string, it raises a ValueError exception.
  

  str = 'Hello World'
  print(str.index("World")) # 6
  

• format()

  Formats the string for printing it to console.
  

  
  name="Mike"
  
  str = 'Hello {}!'
  print(str.format(name)) # Hello Mike!
  
  # We can also do it this way
  str2= f"Hello {name}!"
  print(str2) # Hello Mike!
  

• format_map()

  Formats specified values in a string using a dictionary.
  

  coordinates = {'x':4,'y':-5, 'z': 0}
  print('{x} {y} {z}'.format_map(coordinates)) # 4 -5 0
  

• isalnum()

  Checks whether all the characters in a given string is alphanumeric or not.
  

  str = 'Hello World'
  print(str.isalnum()) # False
  
  str = 'HelloWorld'
  print(str.isalnum()) # True
  
  str = 'HelloWorld1100'
  print(str.isalnum()) # True
  

• isalpha()

  Returns “True” if all characters in the string are alphabets.
  

  str = 'Hello World'
  print(str.isalpha()) # False
  
  str = 'HelloWorld'
  print(str.isalpha()) # True
  
  str = 'HelloWorld1100'
  print(str.isalpha()) # False
  

• isnumeric()

  Returns “True” if all characters in the string are numeric characters.
  

  str = 'Hello World'
  print(str.isnumeric()) # False
  
  str = '12131'
  print(str.isnumeric()) # True
  

• isdecimal()

  Returns true if all characters in a string are decimal.
  

  str = 'Hello World'
  print(str.isdecimal()) # False
  
  str = '1234567'
  print(str.isdecimal()) # True
  
  str = '9866asdf3s'
  print(str.isdecimal()) # False
  

• isdigit()

  Returns “True” if all characters in the string are digits.
  

  str = '1234567'
  print(str.isdigit()) # True
  
  str = '9866asdf3s'
  print(str.isdigit()) # False
  

• isidentifier()

  The isidentifier() method returns True if the string is a valid identifier in Python.
  

  str = 'Hello World'
  print(str.isidentifier()) # False
  
  str = 'while'
  print(str.isidentifier()) # True
  
  str = 'Python'
  print(str.isidentifier()) # True
  

• isprintable()

  Returns “True” if all characters in the string are printable or the string is empty.
  

  str = 'Hello World'
  print(str.isprintable()) # True
  
  str = 'Hello World\n'
  print(str.isprintable()) # False
  

• isspace()

  Returns “True” if all characters in the string are whitespace characters.
  

  s = '   \t'
  print(s.isspace()) # True
  
  s = ' a '
  print(s.isspace()) # False
  
  s = ''
  print(s.isspace()) # False
  

• join()

  The string join() method returns a string by joining all the elements of an iterable (list, string, tuple), separated by the given separator.
  

  text = ['Python', 'is', 'a', 'fun', 'programming', 'language']
  print(' '.join(text)) # Python is a fun programming language
  print('_'.join(text)) # Python_is_a_fun_programming_language
  

• ljust()

  Left aligns the string according to the width specified
  

• lstrip()

  Returns the string with leading characters removed
  

• maketrans()

  Returns a translation table
  

• partition()

  Splits the string at the first occurrence of the separator
  

• replace()

  Replaces all occurrences of a substring with another substring
  

• rfind()

  Returns the highest index of the substring
  

• rindex()

  Returns the highest index of the substring inside the string
  

• rjust()

  Right aligns the string according to the width specified
  

• rpartition()

  Split the given string into three parts
  

• rsplit()

  Split the string from the right by the specified separator
  

• rstrip()

  Removes trailing characters
  

• splitlines()

  Split the lines at line boundaries
  

• startswith()

  Returns “True” if a string starts with the given prefix
  

• strip()

  Returns the string with both leading and trailing characters
  

• translate()

  Modify string according to given translation mappings
  

• zfill()

  Returns a copy of the string with ‘0’ characters padded to the left side of the string
  

Reference

• https://docs.python.org/3/library/string.html
• https://www.geeksforgeeks.org/python-string-methods/
• https://www.programiz.com/python-programming/methods/string