Regular Expression in Python

Anh-Thi Dinh
We can select string with some patterns.

Import library

1import re

Special characters

  • . matches any character except a newline
  • ^a all strings starting with 'a'
  • a$ all strings ending with 'a'
  • ab+ matches 'ab', 'abb' but not 'a', 'ac'.
  • [bcr]at any characters within [] can be filled the space
  • Using \\ to escape special characters
    • \\s : whitespace characters. \\S: any except whitespace.
    • \\b : empty strings (only at the beginning or end of a word). \\B:
  • cat|dog would match 'catfish' and 'hotdog' for begin and end characters
  • [amk] will match 'a', 'm', or `'k``
  • [0-9] will match any character that falls between 0 and 9
  • [a-z] : lowercase
  • [0-9]{4}: repeat the pattern [0-9] four times by writing
  • a{m,n} matches from m to n repetitions of 'a'.
    • a{m,} matches from m to infinity repetitions of 'a'.


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