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How to Split, Reverse, and Join Strings in Python

This guide explains a common string manipulation task in Python: splitting a string into a list of words, reversing the order of those words, and then joining them back into a single string. We'll focus on the most efficient and Pythonic approach using str.split(), slicing for reversal, and str.join().

Splitting, Reversing, and Joining a String​

Here's the most concise and efficient way to split, reverse, and rejoin a string in Python:

my_str = 'tutorial reference com'

my_list = my_str.split(' ')             # 1. Split into a list of words
print(my_list)                          # Output: ['tutorial', 'reference', 'com']

reversed_list = my_list[::-1]           # 2. Reverse using slicing.
print(reversed_list)                    # Output: ['com', 'reference', 'tutorial']

my_str_again = ' '.join(reversed_list)  # 3. Join back into a string
print(my_str_again)                     # Output: com reference tutorial
  • You can also reverse the list in place using the reverse() method.
  • This example uses spaces as the delimiter, however you can use other delimiters.

Understanding the Steps​

Let's break down each step in detail:

Splitting the String (str.split()):​

my_str = 'tutorial reference com'
my_list = my_str.split(' ')                 # Split on spaces
print(my_list)                              # Output: ['tutorial', 'reference', 'com']

# Example with a different delimiter:
my_str_comma = 'tutorial,reference,com'
my_list_comma = my_str_comma.split(',')     # Split on commas
print(my_list_comma)                        # Output: ['tutorial', 'reference', 'com']
  • my_str.split(' '): The split() method divides the string into a list of substrings. The argument to split() is the delimiter. If you don't provide an argument, it splits on whitespace (spaces, tabs, newlines).

Reversing the List (Slicing)​

The most efficient way to reverse a list without modifying the original is to use slicing with a step of -1:

my_list = ['tutorial', 'reference', 'com']
reversed_list = my_list[::-1]   # Reverse using slicing
print(reversed_list)            # Output:['com', 'reference', 'tutorial']
print(my_list)                  # Output:['tutorial', 'reference', 'com']
  • my_list[::-1]: Creates a reversed copy of the list. The original my_list is unchanged.
  • The [::-1] slice creates a reversed copy of the list.
  • If you want to reverse the list in place using my_list.reverse(), you can do that as well, but that will change the my_list variable:
my_list = ['tutorial', 'reference', 'com']
my_list.reverse()   # Reverse IN PLACE
print(my_list)      # Output: ['com', 'reference', 'tutorial']

Joining the List (str.join()):​

my_list = ['tutorial', 'reference', 'com']

my_list.reverse()
print(my_list)        # Output: ['com', 'reference', 'tutorial']

my_str_again = ' '.join(my_list)
print(my_str_again)   # Output: com reference tutorial

my_str_again = ','.join(my_list)
print(my_str_again)   # Output: com,reference,tutorial

my_str_again = ''.join(my_list)
print(my_str_again)   # Output: comreferencetutorial
  • ' '.join(reversed_list): The join() method takes an iterable (like a list) of strings and concatenates them into a single string. The string you call join() on (in this case, a space: ' ') is used as the separator between the elements.
  • You can use any separator you want (e.g., ',', '-', or even '' for no separator).

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