As the title says, I wanted a python program that changes the file name, but I wanted to overwrite if there already is a file with that destination name.

import os, sys

original = sys.argv[1]
output = sys.argv[2]

os.rename(original, output)

But my code just shows me this error when there already is file with that destination name.

  os.rename<original, output>
WindowsError: [Error 183] Cannot create a file when that file already exists

What fix should I make?

On Windows os.rename won't replace the destination file if it exists. You have to remove it first. You can catch the error and try again after removing the file:

import os

original = sys.argv[1]
output = sys.argv[2]

try:
    os.rename(original, output)
except WindowsError:
    os.remove(output)
    os.rename(original, output)