KING

regular expression

• use the match string
  • but not all the string can be matched

basic character in python

1

import re

• ordinary character
  • like re’test’ will match the string test
• oral character
  • like . ^ $ * + ? {} [] \ | ()
  • like []
    • use to direct to a range of the string set
    • s = r'abc' re.findall(s, "aaaaaaaabc") //use [] rt = "top tip tap twp tep" r1 = r"t[io]p" re.findall(r1, rt) //output ['top'], ['tip'] r2 = r"t[^io]p" re.findall(r2, rt) //output ['tap'],['tep'], ['twp']
    • and oral character is no use in the []
    • also can use r'0-3' replace r'0123'
      • use ‘r’[0-3a-cA-C]‘’ replace r'[0123abcABC]'
  • like ^
    • use the match the head of the line
    • s = r'^t' st = 'tss' //output ['t']
  • like $
    • use to match the end of the line
  • like \
    • used if you want to transform the oral character into a original one
    • use ‘^’ to make ^ as a original character
    • and can be used as
      • \d match [0-9]
      • \D match [^0-9]
      • \s match [\t\n\r\f\v]
        • means and empty character
      • \S match [^\t\n\r\f\v]
        • means non empty character
      • \w match [a-zA-Z0-9]
      • \W match [^a-zA-Z0-9]
  • like *
    • match multiple character
    • means repeat the character in front of the * for 0-many times
    • r = r'ab*' rt = 'abbbbbb' re.findall(r, rt) //output['abbbbbb']
  • like +
    • match the charter that appear more than one time
  • like ?
    • match the charter that appear zero or one time
    • can be used as minimum match
      • r = r'ab+?'
      • rt = 'abbbbbb'
      • output the ab
  • like the {}
    • means that the character can be repeat how many times
    • r = r'a{1,3}' rt = 'aaaaa' then can match a, aa, aaa
    • {0,} == *
    • {1,} == +
    • {0,1} == ?

functions

• compile the expression to speed up
  • r = r'\d{3,4}-?\d{8}' p_telephone = re.compile(r) p_telephone.findall('010-12345678') //output ['010-12345678']
  • and you can add attribute while compile

• there are some normal functions

  • match
    • only search from the front
    • p_telephone.match('o010-12345678') //output nothing because the 010-12345678 is not start from the begin
  • search
    • search the whole string
    • no matter where the number is , if you can find it, you can find it.
  • findall
  • finditer
    • the same as findall but you need to use iter so that you can get the value

• and there are sub(), subn(), split()

  • sub()
    • r = r'c..t' re.sub(r, 'aaa', 'caat cast cccc') //output 'aaa aaa cccc'
  • subn()
    • the difference between sub and subj is that subj provide a count of the how many stuff you replace
    • r = r'c..t' re.subn(r, 'aaa', 'caat cast cccc') //output 'aaa aaa cccc', 2
  • split()
    • split the string using a regular express
    • re.split(r'[\+\*\-]', '1+2-3*5') //output ['1', '2', '3', '5']
  • use dir(re) to see what functions re have

flags in re module

devision

• ()
• email = r'\w{3}@\w+(\.com|\.cn)'
• use the () to divide the .com and .cn
• so that we can use the regular form to match email address