Python regex to replace double backslash with single backslash

Question

I'm trying to replace all double backslashes with just a single backslash. I want to replace 'class=\\"highlight' with 'class=\"highlight'. I thought that python treats '\\' as one backslash and r'\\+' as a string with two backslashes. But when I try

In [5]: re.sub(r'\\+', '\\', string)
sre_constants.error: bogus escape (end of line)

So I tried switching the replace string with a raw string:

In [6]: re.sub(r'\\+', r'\\', string)
Out [6]: 'class=\\"highlight'

Which isn't what I need. So I tried only one backslash in the raw string:

In [7]: re.sub(r'\\+', r'\', string)
SyntaxError: EOL while scanning string literal

@summea sorry this doesn't help: re.sub('\\\\', '\\', string) just gives me 'adfd\\"adfadf' and re.sub('\\\\', '\', string) gives me an EOL SyntaxError — mill
– mill, Commented May 21, 2013 at 15:47
@summea no, that actually looks like a duplicate answer as the last one you posted — mill
– mill, Commented May 21, 2013 at 15:58

Inbar Rose · Accepted Answer · 2013-05-21 15:42:46Z

17

why not use string.replace()?

>>> s = 'some \\\\ doubles'
>>> print s
some \\ doubles
>>> print s.replace('\\\\', '\\')
some \ doubles

Or with "raw" strings:

>>> s = r'some \\ doubles'
>>> print s
some \\ doubles
>>> print s.replace('\\\\', '\\')
some \ doubles

Since the escape character is complicated, you still need to escape it so it does not escape the '

answered May 21, 2013 at 15:42

Inbar Rose

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6 Comments

mill Over a year ago

This works with the print, but not without it. print s.replace('\\\\', '\\') => some \ doubles . But s.replace('\\\\', '\\') => some \\ doubles

Inbar Rose Over a year ago

string.replace() returns the object, you would have to to s = s.replace()

mill Over a year ago

Sorry, this doesn't work. original_string = 'class=\\"highlight'; new_string = original_string.replace('\\\\', '\\'); new_string => 'class=\\"highlight'. The print statement removes the double backslash, not the replace. In fact, just doing print original_string => 'class=\"highlight', as well as print new_string => 'class=\"highlight'. You can also confirm this with new_string == original_string => True

summea Over a year ago

@mill Wouldn't you still need the backslash to be escaped in the actual string/variable? :) Otherwise... how would it know you wanted a backslash left in the final string/variable result...?

musca999 Over a year ago

How did this get a checkmark if it doesn't work. @mill is correct in saying it only works with the print. Still can't find simple solution to this other than maybe analyzing each byte programmatically.

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Ruben · Accepted Answer · 2021-08-03 08:16:19Z

3

Just use .replace() twice!

I had the following path: C:\\Users\\XXXXX\\Desktop\\PMI APP GIT\\pmi-app\\niton x5 test data

To convert \ to single backslashes, i just did the following:

path_to_file = path_to_file.replace('\\','*')
path_to_file = path_to_file.replace('**', '\\')

first operation creates ** for every \ and second operation escapes the first slash, replacing ** with a single \.

Result:

C:**Users**z0044wmy**Desktop**PMI APP GIT**pmi-app**GENERATED_REPORTS
C:\Users\z0044wmy\Desktop\PMI APP GIT\pmi-app\GENERATED_REPORTS

answered Aug 3, 2021 at 8:16

Ruben

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Comments

mogul · Accepted Answer · 2013-05-21 15:50:54Z

2

You only got one backslash in string:

>>> string = 'class=\\"highlight' 
>>> print string
class=\"highlight

Now lets put another one in there

>>> string = 'class=\\\\"highlight' 
>>> print string
class=\\"highlight

and then remove it again

>>> print re.sub('\\\\\\\\', r'\\', string)
class=\"highlight

answered May 21, 2013 at 15:50

mogul

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Comments

BuJay · Accepted Answer · 2021-05-11 13:24:17Z

0

I just realized that this might be the simplest answer:

import os
os.getcwd()

The above outputs a path with \ (2 back slashes)

BUT if you wrap it with a print function, i.e., print(os.getcwd()) it will output the 2 slashes with 1 slash so you can then copy and paste into an address bar!

answered May 11, 2021 at 13:24

BuJay

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