String Reverse
This page was last reviewed on Nov 19, 2021.
Dot Net Perls
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.
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.
List Comprehension
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.
Detail We invoke the list's reverse() method on the characters list. This changes the order of the letters in-place.
Detail We join the characters together on an empty delimiter. This concatenates the chars into a new, reversed string.
String join
def reverse_string(value): # Get characters from the string. characters = [c for c in value] # Reverse list of characters. characters.reverse() # Join characters back into string with empty delimiter. return "".join(characters) # Test our string reversal method. test1 = "cat" reversed1 = reverse_string(test1) print(test1) print(reversed1) test2 = "abcde" reversed2 = reverse_string(test2) print(test2) print(reversed2)
cat tac abcde edcba
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.
String List
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.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Nov 19, 2021 (edit link).
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