Commenting Regular expressions in python

Question

This answer to a question regarding the maintainability of regular expressions mentions the ability of .NET users to implement comments in their regular expressions (I am particularly interested in the second example)

Is there an easy native way to reproduce this in python, preferably without having to install a third party library or writing my own comment-strip algorithm?

what I currently do is similar to the first example in that answer, I concatenate the regular expression in multiple lines and comment each line, like in the following example:

    regexString  =  '(?:' # Non-capturing group matching the beginning of a comment
    regexString +=      '/\*\*'
    regexString +=  ')'

Using named groups can also help in the readability of your regex code. — nfazzio
– nfazzio, Commented Dec 18, 2013 at 21:53

Wieland · Accepted Answer · 2013-12-18 21:45:26Z

18

You're looking for the VERBOSE flag in the re module. Example from its documentation:

a = re.compile(r"""\d +  # the integral part
                   \.    # the decimal point
                   \d *  # some fractional digits""", re.X)

answered Dec 18, 2013 at 21:45

Wieland

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1 Comment

kindall Over a year ago

You can also specify this flag in the regex itself by putting (?x) at the beginning.

Vasili Syrakis · Accepted Answer · 2013-12-18 21:54:11Z

5

r"""
(?:      # Match the regular expression below
   /        # Match the character “/” literally
   \*       # Match the character “*” literally
   \*       # Match the character “*” literally
)
"""

You can also add comments into regex like this:

(?#The following regex matches /** in a non-capture group :D)(?:/\*\*)

answered Dec 18, 2013 at 21:54

Vasili Syrakis

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