The function prototype of re.sub is: re.sub(pattern, repl, string, count)

The second function is the replaced string; in this case it is '-'

The fourth parameter refers to the number of replacements. Defaults to 0, meaning every match is replaced.

re.sub also allows sophisticated handling of replacement of matches using functions. For example: re.sub(r'\s', lambda m: '[' m.group(0) ']', text, 0); Replace the space ' ' in the string with '[ ]'.

re.split

You can use re.split to split a string, such as: re.split(r'\s ', text); split the string into a word list by spaces.

re.findall

re.findall can get all matching strings in the string. For example: re.findall(r'\w*oo\w*', text); Get all words containing 'oo' in the string.

re.compile

Regular expressions can be compiled into a regular expression object. Frequently used regular expressions can be compiled into regular expression objects, which can improve certain efficiency.