Changing strings in files

Tue Nov 10 01:24:44 EST 2020

I have a situation where in a directory tree I want to change a certain
string in all files where that string occurs.
My idea was to do
- os.scandir and for each file
 - check if a file is a text file
 - if it is not a text file skip that file
 - change the string as often as it occurs in that file
What is the best way to check if a file is a text file? In a script I
could use the `file` command which is not ideal as I have to grep the
result. In Perl I could do -T file.
How to do best in Python?
-- 
Thanks,
Manfred