Last Updated : 28 Apr, 2025
Given a text file. The task is to reverse a single line of user's choice from a given text file and update the already existing file. Examples:
Input:
Hello Geeks
for geeks!
User choice = 1
Output:
Hello Geeks
geeks! for
Input:
This is a geek
Welcome to GeeksforGeeks
GeeksforGeeks is a computer science portal
User choice = 0
Output:
geek a is This
Welcome to GeeksforGeeks
GeeksforGeeks is a computer science portal
Implementation: Let's suppose the text file looks like this -
Python3
# Open file in read mode
f = open('GFG.txt', 'r')
# Read the content of the
# file and store it in a list
lines = f.readlines()
# Close file
f.close()
# User's choice
choice = 1
# Split the line into words
line = lines[choice].split()
# line is reversed
Reversed = " ".join(line[::-1])
# Updating the content of the
# file
lines.pop(choice)
lines.insert(choice, Reversed)
# Open file in write mode
u = open('GFG.txt', 'w')
# Write the new content in file
# and note, it is overwritten
u.writelines(lines)
u.close()
Output:
Time complexity: O(n), where n is the number of lines in the file.
Auxiliary space: O(n), where n is the number of lines in the file.
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