Question

With this code I get:

newContent='asdf asdf \nOUTPUT_DIRECTORY       = working\topOnly'

I’d expect it to be:

newContent='asdf asdf \nOUTPUT_DIRECTORY       = working\\topOnly'

The reg ex is stripping out a """\""" between """working""" and """topOnly""". If I do something like """valStr = 'working\\ytopOnly'""" then it works as expected.

What do I need to change in my code so that it was as expected?

import re

valStr = 'working\\topOnly'
cmdFileContent = 'asdf asdf \nOUTPUT_DIRECTORY       = asdf'
name = 'OUTPUT_DIRECTORY'

varRegEx = r"""
    (\n          #match new line
    %s            #var
    \s*           #skip white spaces
    =
    \s?)          #skip white spaces
    (.*)          #match and store rest of line
    """%name

newContent  = re.compile(varRegEx, re.VERBOSE).sub(r'\1%s'%valStr, cmdFileContent)

Answer 1

The help for re.sub says:

repl can be either a string or a callable; if a string, backslash escapes in it are processed.

Since it’s doing its own layer of processing escapes, you will need another layer of escapes:

newContent = re.compile(varRegEx, re.VERBOSE).sub(r'\1%s'%valStr.replace('\\', '\\\\'), cmdFileContent)