Python3 regular expressions
Python uses re library for regular expressions. re comes with standard python installation. Regular expressions is a very big topic. This page only covers the basics of how to search and substitute. The syntax for patterns is the same as Perl. Consider the following example:
import re line = "apple banana carrot date eggplant fig guava" # is there a match? if re.search("carrot", line): print('match found') else: print('match not found') # what was matched? mat = re.search(r'(.*) date (.*)', line) if mat: print(mat.group()) print(mat.group(1)) print(mat.group(2)) else: print('no') # how to match and substitute a substring res = re.sub(r'guava', "grapefruit", line) if res: print(res) else: print('not substitution')
match found apple banana carrot date eggplant fig guava apple banana carrot eggplant fig guava apple banana carrot date eggplant fig grapefruit
First, we need to import re. The two function of re that we are interested in a re are search and sub. Search finds the substring (m// in Perl). sub finds and substitutes the substring with another (s/// in Perl).