Question

code goes below:

line = r'abc\def\n'
rline = re.sub('\\\\', '+', line) # then rline should be r'abc+def+n'

Apparently, I just want to replace the backslashes in line with ‘+’.
What I thought was that a backslash in line can be expressed as ‘\’, then why should I use ‘\\’ to get the re.sub work right.

I’m confused.

Answer 1

Because there are two levels of backslashing:

1. re.sub uses \ as an escape
2. Python uses \ as an escape (unless you do r’…’)

So \\\\ (python) -> \\ (re.sub) -> \

EDIT

And the SO level of backslashing! (it got me!)