Reverse the characters in a string. Use list comprehension, reverse and the join method.
Reverse string. Programs sometimes have unusual requirements. For example we might need to reverse the characters in a string. This could help for generating a unique key from some data.Strings
With list comprehension, we get the characters of a string. And then we can reverse those characters with reverse() and call join() to join them back again.
Example def. Here we introduce a reverse_string method. This method receives a string and returns a reversed form of it. We first use list comprehension to get a character list.
Tip: With a list of characters, returned by the list comprehension, we can manipulate the ordering of the characters.
Reverse: We invoke the list's reverse() method on the characters list. This changes the order of the letters in-place.
Join: We join the characters together on an empty delimiter. This concatenates the chars into a new, reversed string.
Python program that implements string reverse method
# Get characters from the string.
characters = [c for c in value]
# Reverse list of characters.
# Join characters back into string with empty delimiter.
# Test our string reversal method.
test1 = "cat"
reversed1 = reverse_string(test1)
test2 = "abcde"
reversed2 = reverse_string(test2)
Some concepts. Lists are powerful in Python. We can reverse them. With a list comprehension, meanwhile, we can quickly construct a list of characters from an expression.ListList Comprehension
So: The trick to manipulating strings is to convert them to lists first. We then just manipulate the list elements.
A review. By reversing strings, we learn how to manipulate strings in many ways. We can change the individual characters, or reorder the characters in any fashion. This is powerful.