When doing a search and replace of strings that contain '/', ie: URLs, sed and or printf make not always work. Use this.

replace_inline_infile.py

import argparse

#
# Long story short, using sed/printf does always handle strings that contain '/' them (e.g.: urls)
#

parser = argparse.ArgumentParser()
parser.add_argument('fileToSearch', type=file)
parser.add_argument('textToSearch', type=str)
parser.add_argument('textToReplace', type=str)
args = parser.parse_args()

with open(args.fileToSearch.name, 'r') as file:
  filedata = file.read()

filedata = filedata.replace(args.textToSearch, args.textToReplace)

with open(args.fileToSearch.name, 'w') as file:
  file.write(filedata)

Initially, based on a stackoverflow answer, I used the fileinput(?) lib, but heard a number of corrections stating that the above solution is better, unless you're dealing with a large file.