Swap elements in String list - Python
Last Updated :
17 Apr, 2025
Swapping elements in a string list means we need to exchange one element with another throughout the entire string list in Python. This can be done using various methods, such as using replace(), string functions, regular expressions (Regex), etc. For example, consider the original list: ['Gfg', 'is', 'best', 'for', 'Geeks']. After performing swap, the list becomes: ['efg', 'is', 'bGst', 'for', 'eGGks'].
Using Replace
This method uses Python’s replace() function to swap characters in each string of the list. It replaces one character with another and can be applied iteratively on each element.
Python
a = ['Gfg', 'is', 'best', 'for', 'Geeks']
print(str(a))
res = [sub.replace('G', '-').replace('e', 'G').replace('-', 'e') for sub in a]
print (str(res))
Output['Gfg', 'is', 'best', 'for', 'Geeks']
['efg', 'is', 'bGst', 'for', 'eGGks']
Explanation: In this code, the replace() function is chained to replace 'G' with '-', 'e' with 'G', and '-' with 'e'. The list comprehension applies this transformation to each element of the list, and the result is stored in the res list. The original and transformed lists are printed before and after the operation.
Using String Functions
This method uses Python's string manipulation functions like join(), replace(), and split() to perform the element swap. The list is first joined into a string, transformed, and then split back into a list.
Python
a = ['Gfg', 'is', 'best', 'for', 'Geeks']
print(str(a))
res = ", ".join(a)
res = res.replace("G", "_").replace("e", "G").replace("_", "e").split(', ')
print (str(res))
Output['Gfg', 'is', 'best', 'for', 'Geeks']
['efg', 'is', 'bGst', 'for', 'eGGks']
Explanation: The code joins the list into a single string using ", ".join(a). It then applies replace() to swap characters ('G' to '', 'e' to 'G', and '' to 'e'). Finally, the string is split back into a list using split(', '), and the result is stored in res. This method is efficient for handling string-based swaps in a list.
Using RegEx
This method uses regular expressions (RegEx) to perform the character swaps within the list elements. It's a more advanced approach suited for complex pattern-based replacements.
Python
import re
a = ['Gfg', 'is', 'best', 'for', 'Geeks']
print(str(a))
res = [re.sub('-', 'e', re.sub('e', 'G', re.sub('G', '-', sub))) for sub in a]
print(str(res))
Output['Gfg', 'is', 'best', 'for', 'Geeks']
['efg', 'is', 'bGst', 'for', 'eGGks']
Explanation: The code utilizes the re.sub() function, applying nested substitutions to first replace 'G' with '-', then 'e' with 'G', and finally '-' with 'e'. This RegEx-based approach allows for more flexible and powerful pattern matching and substitution, especially when dealing with more complex replacement scenarios. The result is stored in res and printed.
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