Category: Python

. – Any Character Except New Line
\d – Digit (0-9)
\D – Not a Digit(0-9)
\w – Word Character (a-z, A-Z, 0-9, _)
\W – Not a Word Character
\s – Whitespace (space, tab, newline)
\S – Not Whitespace (space, tab, newline)

\b – Word Boundary
\B – Not a Word Boundary
^ – Beginning of a String
$ – End of a String

[] – Mathes Characters in brackets
[^ ] – Matches Characters NOT in bracket
| – Either Or
( ) – Group

Quantifiers:
* – 0 or More
+ – 1 or More
? – 0 or One
{3} – Exact Number
{3,4} – Range of Numbers (Minimum, Maximum)