Getting Started with Python re library (regular expression)

Regular Expressions (English name: regular expression,regex,re) are expressions that are used to succinctly Express a set of character strings. The most important applications are in string matching.

syntax for regular expressions -common operators:

Operator	Description	Instance
.	Represents any single character
[ ]	Character set, giving a range of values to a single character	[ABC] means a, B, c,[a-z] represents a to Z single character
[^ ]	Non-character sets, exclusion ranges for individual characters	[^ABC] Represents a single character that is not a or B or C
*	Previous character 0 or unlimited expansion	abc* means AB, ABC, ABCC, ABCCC, etc.
+	Previous character 1 or unlimited expansion	abc+ means ABC, ABCC, ABCCC, etc.
?	The previous character 0 or 1 times extended	Abc? Represents AB, ABC,
|	Left and right expression any one	Abc|def means ABC, DEF
{m}	Extend one character m times	Ab{2}c says ABBC
{M,n}	Extend one character M to n times (with N)	Ab{1,2}c means ABC, ABBC
^	Match string start	^ABC represents ABC and at the beginning of a string
$	Match string End	abc$ represents ABC and at the end of a string
( )	Grouping tags, which can only be used internally | Operator	(ABC) means ABC, (ABC|DEF) means ABC, DEF
\d	number, equivalent to [0-9]
\w	Word character, equivalent to [a-za-z0-9]

Regular expression that matches the IP address:

Regular expressions in the form of IP address strings (IP address divided into 4 segments, 0-255 per segment)

Exact wording 0-99:[1-9]?\d

100-199:1\d{2}

200-249:2[0-4]\d

250-255:25[0-5]

([1-9]?\d| 1\D{2}| 2[0-4]\d| 25[0-5]).) {3} ([1-9]?\d| 1\D{2}| 2[0-4]\d| 25[0-5])

Getting Started with Python re library (regular expression)