Python regex escape special characters

Does Python have a function that I can use to escape special characters in a string?

For example, I'm "stuck" :\ should become I\'m \"stuck\" :\\.

poke

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asked Nov 17, 2010 at 8:09

5

Use re.escape

>>> import re
>>> re.escape(r'\ a.*$')
'\\\\\\ a\\.\\*\\$'
>>> print(re.escape(r'\ a.*$'))
\\\ a\.\*\$
>>> re.escape('www.stackoverflow.com')
'www\\.stackoverflow\\.com'
>>> print(re.escape('www.stackoverflow.com'))
www\.stackoverflow\.com

Repeating it here:

re.escape(string)

Return string with all non-alphanumerics backslashed; this is useful if you want to match an arbitrary literal string that may have regular expression metacharacters in it.

As of Python 3.7 re.escape() was changed to escape only characters which are meaningful to regex operations.

answered Nov 17, 2010 at 8:13

pyfuncpyfunc

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2

I'm surprised no one has mentioned using regular expressions via re.sub():

import re
print re.sub(r'([\"])',    r'\\\1', 'it\'s "this"')  # it's \"this\"
print re.sub(r"([\'])",    r'\\\1', 'it\'s "this"')  # it\'s "this"
print re.sub(r'([\" \'])', r'\\\1', 'it\'s "this"')  # it\'s\ \"this\"

Important things to note:

• In the search pattern, include \ as well as the character(s) you're looking for. You're going to be using \ to escape your characters, so you need to escape that as well.
• Put parentheses around the search pattern, e.g. ([\"]), so that the substitution pattern can use the found character when it adds \ in front of it. (That's what \1 does: uses the value of the first parenthesized group.)
• The r in front of r'([\"])' means it's a raw string. Raw strings use different rules for escaping backslashes. To write ([\"]) as a plain string, you'd need to double all the backslashes and write '([\\"])'. Raw strings are friendlier when you're writing regular expressions.
• In the substitution pattern, you need to escape \ to distinguish it from a backslash that precedes a substitution group, e.g. \1, hence r'\\\1'. To write that as a plain string, you'd need '\\\\\\1' — and nobody wants that.

answered Aug 17, 2012 at 19:35

Tim RuddickTim Ruddick

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Use repr()[1:-1]. In this case, the double quotes don't need to be escaped. The [-1:1] slice is to remove the single quote from the beginning and the end.

>>> x = raw_input()
I'm "stuck" :\
>>> print x
I'm "stuck" :\
>>> print repr(x)[1:-1]
I\'m "stuck" :\\

Or maybe you just want to escape a phrase to paste into your program? If so, do this:

>>> raw_input()
I'm "stuck" :\
'I\'m "stuck" :\\'

answered Nov 17, 2010 at 9:03

4

As it was mentioned above, the answer depends on your case. If you want to escape a string for a regular expression then you should use re.escape(). But if you want to escape a specific set of characters then use this lambda function:

>>> escape = lambda s, escapechar, specialchars: "".join(escapechar + c if c in specialchars or c == escapechar else c for c in s)
>>> s = raw_input()
I'm "stuck" :\
>>> print s
I'm "stuck" :\
>>> print escape(s, "\\", ['"'])
I'm \"stuck\" :\\

answered Aug 1, 2013 at 17:34

spatarspatar

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If you only want to replace some characters you could use this:

import re

print re.sub(r'([\.\\\+\*\?\[\^\]\$\(\)\{\}\!\<\>\|\:\-])', r'\\\1', "example string.")

answered Feb 13, 2015 at 8:22

Note: This answer was written in response to the original question which was written in a way that it asked for a generic “function which can [be used] to escape special characters”, without specifying that these would be used for regular expressions, and without further specifying what special characters would have to be escaped.

In order to escape an arbitrary set of “special characters”, you can write a custom function that replaces each of these characters with an escaped variant. Something like this:

def escapeSpecialCharacters ( text, characters ):
    for character in characters:
        text = text.replace( character, '\\' + character )
    return text

>>> escapeSpecialCharacters( 'I\'m "stuck" :\\', '\'"' )
'I\\\'m \\"stuck\\" :\\'
>>> print( _ )
I\'m \"stuck\" :\

answered Nov 17, 2010 at 8:15

pokepoke

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1

use json:

import json
print(r"""(I'm "stuck" :\)""")               # (I'm "stuck" :\)
print(json.dumps(r"""(I'm "stuck" :\)"""))   # (I'm "stuck" :\)

for json to string with escape character

json.dumps(json.dumps(d))

answered Jul 24 at 9:56

lbsweeklbsweek

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