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 +=  ')'

Yes, see the [verbose flag](http://docs.python.org/2/library/re.html#re.VERBOSE) in the `re` module. — BrenBarn, Dec 18 '13 at 21:42
Using [named groups](http://docs.python.org/2/howto/regex.html#non-capturing-and-named-groups) can also help in the readability of your regex code. — nfazzio, Dec 18 '13 at 21:53

score 17 · Accepted Answer · answered Dec 18 '13 at 21:45

17

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 '13 at 21:45

Wieland

1,663
14
23

8

You can also specify this flag in the regex itself by putting `(?x)` at the beginning. – kindall Dec 18 '13 at 21:57

score 3 · Answer 2 · answered Dec 18 '13 at 21:54

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)(?:/\*\*)

Commenting Regular expressions in python

2 Answers2

Linked