Searching for a file

It occurs to me that it might be useful if Python provided a function to 
search for a file with a given name in various directories (much as the 
import.import_lib function searches for a module in the directories in 
sys.path).
This function would perhaps be best placed in the os.path or os modules.
To start the ball rolling, I offer this version:

import sys
import os

def findfile(fileName, *PathLists):
     if not PathLists:
         # Default to searching just sys.path:
         PathLists = [ sys.path ]
         # This may or may not be the most useful default;
         # there is a case for having no default, forcing calls of this 
function
         # to explicitly specifiy which paths they want to search,
         # and perhaps raise an Exception if they don't;
         # suggestions welcome.

     for pList in PathLists:
         # if pList is a str, assume it is a semicolon-separated list of 
directories
         # (like the PATH and PYTHONPATH environment variables);
         # otherwise assume it is a sequence of paths (like sys.path):
         if isinstance(pList, str):
             pList = pList.split(';')

         for path in pList:
             filePath = os.path.join(path, fileName)
             if os.path.isfile(filePath):
                 return filePath
                 # Return first match found.
                 # Another possibility is to return a list of all matches.
     return None

Then e.g.
     print(findfile('os.py'))
would print something like
     C:\Python311\Lib\os.py

This idea was partly inspired by Michael Stemper asking about best 
practice for placing, and finding, a configuration file.
Thoughts?

Best wishes
Rob Cliffe
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