Python Learning--common regular expression collation

1. Predefined character set (can be used in [])

\d: Number [0-9] \d: Non-numeric \s: white space character \s: non-whitespace character \w: alphanumeric underline [a-za-z0-9_] \w: Non (alphanumeric underline)

2. Number of words (used in characters or ())

*: Match the previous character 0 or unlimited ab* a,abbbb

+: Matches the previous character one or more times.

？ : matches the previous character 0 or 1 times.

{m}: matches the previous character m times.

{M,n}: matches the previous character at least m times, up to N times.

3. Boundary Matching

^: Match string beginning $; Match string end

Python Learning--common regular expression collation