anton wrote:
> I want to replace all occourences of " by \" in a string.
>
> But I want to leave all occourences of \" as they are.
>
> The following should happen:
>
> this I want " while I dont want this \"
>
> should be transformed to:
>
> this I want \" while I dont want this \"
>
> and NOT:
>
> this I want \" while I dont want this \\"
>
> I tried even the (?<=...) construction but here I get an unbalanced
> paranthesis error.
>
> It seems tha re is not able to do the job due to parsing/compiling
> problems for this sort of strings.
>
>
> Have you any idea??
The problem is underspecified. Should r'\\"' become r'\\\"' or remain
unchanged? If the backslash is supposed to escape the following letter
including another backslash -- that can't be done with regular expressions
alone:
# John's proposal:
>>> print re.sub(r'(?<!\\)"', r'\"', 'no " one \\", two \\\\"')
no \" one \", two \\"
One possible fix:
>>> parts = re.compile("(\\\\.)").split('no " one \\", two \\\\"')
>>> parts[::2] = [p.replace('"', '\\"') for p in parts[::2]]
>>> print "".join(parts)
no \" one \", two \\\"
Peter
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