Escaping regex string Escaping regex string python python

Escaping regex string


Use the re.escape() function for this:

4.2.3 re Module Contents

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.

A simplistic example, search any occurence of the provided string optionally followed by 's', and return the match object.

def simplistic_plural(word, text):    word_or_plural = re.escape(word) + 's?'    return re.match(word_or_plural, text)


You can use re.escape():

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.

>>> import re>>> re.escape('^a.*$')'\\^a\\.\\*\\$'

If you are using a Python version < 3.7, this will escape non-alphanumerics that are not part of regular expression syntax as well.

If you are using a Python version < 3.7 but >= 3.3, this will escape non-alphanumerics that are not part of regular expression syntax, except for specifically underscore (_).


Unfortunately, re.escape() is not suited for the replacement string:

>>> re.sub('a', re.escape('_'), 'aa')'\\_\\_'

A solution is to put the replacement in a lambda:

>>> re.sub('a', lambda _: '_', 'aa')'__'

because the return value of the lambda is treated by re.sub() as a literal string.


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