regex - Clean Python Regular Expressions

Question

Is there a cleaner way to write long regex patterns in python? I saw this approach somewhere but regex in python doesn't allow lists.

patterns = [
    re.compile(r'<!--([^->]|(-+[^->])|(-?>))*-{2,}>'),
    re.compile(r'
+|s{2}')
]

Answer 1

You can use verbose mode to write more readable regular expressions. In this mode:

• Whitespace within the pattern is ignored, except when in a character class or preceded by an unescaped backslash.
• When a line contains a '#' neither in a character class or preceded by an unescaped backslash, all characters from the leftmost such '#' through the end of the line are ignored.

The following two statements are equivalent:

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

b = re.compile(r"d+.d*")

(Taken from the documentation of verbose mode)