Regular expressions for Python

1.re.findall ("A", "AB")

A: Match rule ab: what to match

The result is returned as a list: [' a ']

2. Metacharacters: ".", "^", "$", "*", "+", "?", "{}", "[]", "|", "()", "\"

"." : matches any character except the line break "\ n";

Import= Re.findall ('ab.d',"abcdefg"  = Re.findall ('ab.e',"abcdefg") Print # [' ABCD '] Print # []

"^": Match string start

　　　　

Import= Re.findall ('^ab',"abcdefg"  = Re.findall ('^bc',"abcdefg")  Print#[' AB ']print#[]

' $ ': Match string end

Import= Re.findall ('ab$',"abcdefg"  = Re.findall ('fg$',"abcdefg")  Print#[]print#[' FG ']

"*": match the previous character 0 or unlimited times

Import= Re.findall ('ab*',"abbdefg"  = Re.findall ('ab*',"acdefg")  Print#[' ABB ']print#[' a ']

"+": Match the previous character 1 or unlimited times

"?" : matches the previous character 0 or 1 times

' {n} ': matches the previous character N times

' {n,m} ': matches the previous character N to M (closed interval)

"[AB]": Match A or b

ImportReA= Re.findall ('a[bc]d',"ABCDEFG") B= Re.findall ('a[bc]d',"ABDEFG") C= Re.findall ('a[bc]d',"ACDEFG")PrintA#[]PrintB#[' Abd ']PrintC#[' ACD ']

"\": 1. Backslash followed by meta-character, so that metacharacters remove special functions

2. followed by ordinary characters, creating special functions

3. Strings that match the string corresponding to the reference sequence

Regular expressions for Python