How to implement Python regular expression

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1. Regular expression _ matches single character # regular expression-matches single character import re "" lst = re.findall (regular expression, string) "" # (1) predefined character set #\ d matches numeric strvar = "sdjfklj234&* (& 1" lst = re.findall ("\ d", strvar) print (lst) #\ D matches non-numeric strvar = "YWERsdf78_&" lst = re.findall ("\ D") Strvar) print (lst) #\ w matches letters or numbers or underscores (matches in Chinese are supported in regular functions) strvar = "sadf234_ ^ & *% $^ $% Hello" lst = re.findall ("\ w", strvar) print (lst) #\ W matches non-alphanumeric or underscore strvar = "sadf234_ ^ & *% ^ $% Hello" lst = re.findall ("\ W") Strvar) print (lst) #\ s matches any blank character ("\ t\ n\ r) strvar ="\ r "lst = re.findall ("\ s ", strvar) print (lst) #\ S matches any non-white space character strvar ="\ r 123 blank * ("lst = re.findall ("\ S ") Strvar) print (lst) #\ nmatch a newline character strvar = "" Today's National Day holiday is over, the brothers are full of loads, playing very sleepy, do their best to adjust. "" lst = re.findall (r "\ n", strvar) print (lst) #\ t matches a tab lst = re.findall (r "\ t") Strvar) print (lst) # (2) character group [] matches the characters enumerated in the character group (choose one by default) # lst = re.findall ("[123c]", "a1b2c3d4") # print (lst) print (re.findall ('a [ABC] baud abb acb adb')) # aab abb acbprint (re.findall ('a [0123456789] b') 'a1b a2b a3b acb ayb')) # A1b A2b a3b# optimized writing 0123456789 = > 0-9print (re.findall ('a [0-9] bologna meme A1b a2b a3b acb ayb')) print (re.findall ('a [abcdefg] baked mummy a1b a2b a3b acb ayb adb')) # acb adb# optimized writing abcdefg = > AFI expresses all lowercase letters a-zprint (re.findall ('a [a-g] b') 'a1b a2b a3b acb ayb adb')) print (re.findall ('a [a-z] baud acb ayb adb')) # acb adb aybprint (re.findall ('a [ABCDEFG] baked memoir A1b a2b a3b aAb aDb aYb')) # aAb aDb# optimized writing ABCDEFG = > Amurg expresses all uppercase letters A-Zprint (re.findall ('a [A-G] b') 'a1b a2b a3b aAb aDb aYb') # aAb aDbprint (re.findall ('a [A-Z] baud aAb aDb aYb')) # aAb aDb aYb# Note: the intermediate ascii code of Amurz contains a special symbol print ('a [A-z] b'). 'a1b a2b a3b acb ayb adb a [b') # matches all letters and numbers print (re.findall ('a [a-zA-Z0-9] bchapter acb ayb adb a [b')) print (re.findall ('a [0-9a-zA-Z]] acb ayb adb b aab aAb aWb aqba1b')) # aab aAb aWb aqb a1bprint (re.findall ('a [0-9] [* # /] b') )) # a1/b# ^ appears at the beginning of the character group except. Print (re.findall ('a [^-+ * /] baked, "a% b ccaa*bda&bd") # a% b a&b# matches special characters such as ^ -\ need to be preceded by\ escape strvar = "a ^ c Amurc a\ c" lst = re.findall (r "a [\ ^\ -\] c", strvar) print (lst) print (lst [- 1]) # Note: in order to prevent escape In the regular expression or in the string to be matched, add r to match strvar = r "a\ b" lst = re.findall (r "a\\ b", strvar) print (lst [0]) 2. Regular expression _ matches multiple characters # regular expression-matches multiple characters # (1) quantifier import re'''1)? Match 0 or 1 a 'print (re.findall (' astatabbzab abb aab') # abb ab abb ab'''2) + match 1 or more a 'print (re.findall (' a'ab aaaaaab abb')) # ab aaaaaab ab'''3) * match 0 or more a 'print (re.findall (' a''print') 'b ab aaaaaab abbbbbbb')) # b ab aaaaaab abbbbbbb' 4) {mQuery n} match m to n a' # 1