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Python - String Functions - Changing Case, Location, Counting, Formatting, Checking, Regular Expressions

🐍 Some of the String Functions include the following:


  • .capitalize() 
  • .upper() 
  • .lower() 
  • .title() 
  • .count() 
  • .find() 
  • .center() 
  • .expandtabs() 
  • .isalnum() 
  • .isalpha() 
  • .islower() 
  • .isspace() 
  • .istitle() 
  • .isupper() 
  • .endswith()
  • .split()
  • .partition() 
Let's take an example string and apply all methods on it.
s = 'hello 1st World, 2nd World, and 3rd World.'

Changing case

Capitalize

s.capitalize()
Output:
'Hello 1st world, 2nd world, and 3rd world'
It capitalizes the first letter of the string for that output alone.

Uppercase

s.upper()
Output:
'HELLO 1ST WORLD, 2ND WORLD, AND 3RD WORLD'
It converts entire string into upper-case for that output alone.

Lowercase

s.lower()
Output:
'hello 1st world, 2nd world, and 3rd world'
It converts entire string into lower-case for that output alone.

Location and Counting

Count

s.count('o')
Output:
4
It counts number of occurrences of the string passed in the string 's' and returns the count.
s.count('world')
Output:
3
It counts number of occurrences of the string passed in the string 's' and returns the count.

Find

s.find('o')
Output:
4
Returns the location of the first occurrence of the string passed in the string 's'.
s.find('world')
Output:
10
Returns the location of the first occurrence of the string passed in the string 's'.

Formatting

Center

s.center(50, '#')
Output:
'####hello 1st world, 2nd world, and 3rd world#####'

It adds the character passed, in front and back of the string 's', only if length of string 's' is less than the number passed. Here length of string 's' is 41. So, it added '#' at the beginning and end of the string to make the length as 50. It is only for that particular output. No changes is made to the actual string 's'.

Expand Tab

The expandtabs() method will expand tab notations \t into spaces. For this example we will NOT use the string 's', but a new string with a tab in it represented by \t
'Hello\tWorld'.expandtabs()
Output:

'Hello    World'

Without .expandtabs() the output is 'Hello\tWorld'.

Check Methods

Is Alphabet  or Number | .isalnum()

s.isalnum()
Output:

False

.isalnum() returns True or False. If all characters in the string are either alphabet or string, it will return True, else it will return False. The example string also included comma, full-stop, exclamation mark, and space. Thus, it returned False.

Is Alphabet | .isalpha()

s.isalpha()
Output:

False

.isalpha() returns True or False. If all characters in the string are alphabet, it will return True, else it will return False. The example string also included exclamation mark, full-stop, space, and question mark, and numbers. Thus, it returned False.

Is Lower case | .islower()

s.islower()
Output:

False

.islower() returns True or False. If all letters in the string are in lower-case, it will return True, else it will return False. The example string includes some upper case letters, thus it returned False.

Is Space | .isspace()

s.isspace()
Output:

False

.isspace() returns True or False. If all characters in the string are white-spaces, it will return True, else it will return False. The example string includes many non-white-space characters, thus it returned False.

Is Title-case | .istitle()

s.istitle()
Output:

False

.istitle() returns True or False. If all lower-cased words begin with an upper-case character, it will return True, else it will return False. The example string includes many words not beginning with upper-case character, thus it returned False.

Is Upper case | .isupper()

s.isupper()
Output:

False

.isupper() returns True or False. If all letters in the string are in upper-case, it will return True, else it will return False. The example string includes some lower case letters, thus it returned False.

Ends WIth | .endswith()

s.endswith('World.')
Output:

True

.endswith() returns True or False. If the string s ends with the string passed to the function as it is, it will return True, else it will return False. The example string ends with 'World.', thus it returned True. Even the case of all letters must match. If you pass 'world.', it will return false as 'W' is in upper-case in the string s.

Built-in Regualr Expressions

Split | .split()

s.split('or')
Output:

['hello! 1st W', 'ld, 2nd W', 'ld, and 3rd W', 'ld.']

.split() returns a list of parts of the string broken at the string passed, and excluding the string passed. The example string is broken down into parts everywhere an 'or' is encountered and returned in the form of the list. Note that 'or' is excluded in the list.

Partition | .partition()

s.partition('or')
Output:

('hello! 1st W', 'or', 'ld, 2nd World, and 3rd World.')

.partition() returns a tuple of 3 parts. The string is broken down on the first occurrence of the string passed, and three parts are formed - first is the part before the passed string, second is the part of the passed string, and third is the part after the passed string. If the passed string is not encountered in the string, even then it passes a tuple, with first part being the entire string, while second and third part being blank.
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