more readable by allowing you to visually separate logical sections of the

pattern and add comments. Whitespace within the pattern is ignored, except

when in a character class, or when preceded by an unescaped backslash,

or within tokens like ``*?``, ``(?:`` or ``(?P<...>``.

or within tokens like ``*?``, ``(?:`` or ``(?P<...>``. For example, ``(? :``

and ``* ?`` are not allowed.

When a line contains a ``#`` that is not in a character class and is not

preceded by an unescaped backslash, all characters from the leftmost such

``#`` through the end of the line are ignored.