Replacing substring in every file in every directory and subdirectory

Question

I have a framework that is using Python 2.7 and I am currently converting it to python 3. However, there are many files that direct to "C:\Python27... etc" to grab certain scripts. I want to go through every file in every framework directory and subdirectory, and change this substring in the file, "..\Python27..", into Python38. For instance, I have this in a .bat file:

@echo off
setlocal
if not exist .\env27 (
  if not exist C:\Python27\Scripts\virtualenv.exe (
    echo VirtualEnv not found: C:\Python27\Scripts >&2
    exit /b 1
  )
  C:\Python27\Scripts\virtualenv .\env27
 ....

I would want to replace C:\Python27\Scripts\virtualenv.exe into C:\Python38\Scripts\virtualenv.exe

I have tried this code Python - Way to recursively find and replace string in text files, but it works for an exact string and not a substring. This is my code so far:

import os, fnmatch

def findAndReplace(directory, find, replacement):
    for dname, dirs, files in os.walk(directory):
        for fname in files:
            fpath = os.path.join(dname, fname)
            with open(fpath) as f:
                s = f.read()
            s = s.replace(find, replacement)
            with open(fpath, "w") as f:
                f.write(s)

I am wondering how I can replace substrings?

Thank you.

Answer 1

You can use re to search for the text groups you needed. I encourage you to check out the regex documentation for specifics on how to make the patterns needed. If finding specific substrings fitting a pattern was not the issue, please clarify, because that's what I'm getting from this.

import os, re

for root, dirs, files in os.walk('path to directory'):
  for infile in files:
    with open(os.path.join(root, infile)) as in_text:
      contents = in_text.read()
    with open(os.path.join(root, infile), 'w') as out:
      out.write(re.sub(find, replacement, contents))

If there's more specifics to this that I haven't covered, I'm sorry. Just let me know if that's the case, and I'll do my best to address it!