How To Find First And All Matched String Use Python Regex Pattern Object

In this article, i will show you how to use python regular expression module ( python re module ) to parse a string to return the first matched string and all matched strings.

1. Use Python Regular Expression Module To Parse String Steps.

  1. Import re module.
    # import python regular expression parse module.
    import re
  2. Create a re.Pattern object by invoke re.compile function. You should provide a pattern format string to the compile function like below.
    # create the pattern format string.
    pattern_format_string = r'\d\d\d-\d\d\d\d\d\d\d\d'
    
    # create the re.Pattern object use re.compile function.
    reg_pattern = re.compile(pattern_format_string)
  3. To get the first matched string, you should invoke the re.Pattern object’s search function like below.
    # invoke re.Pattern object's search method, pass the string that will be parsed to it.
    search_result = pattern_object.search(string)
    
    # get the first matched string in the result by invoke it's group function.    
    print('search result: ' + search_result.group())
  4. To get all matched string, you should invoke the re.Pattern object’s findall function like below.
    # invoke re.Pattern object's findall method.
    find_all_result = pattern_object.findall(string)
       
    print('find all result: ' + str(find_all_result))

2. Python Regular Expression Examples.

There are 2 function in this example, one invoke re.Pattern‘s search function, the other invoke re.Pattern‘s findall function. You can see code comments for detail explanation.

'''
Created on Sep 22, 2020

@author: songzhao
'''
# import python regular expression parse package.
import re

''' 

   This function will invoke the python regexo Pattern object's search method to get the first matched string.

'''
def regexp_search_function(pattern, string):
    
    searched_result = pattern.search(string)
    
    print('search phone number result: ' + searched_result.group()) 
   
''' 

   This function will invoke the python regexo Pattern object's findall method to get all the matched string in a list.

'''    
def regexp_find_all_function(pattern, string):
    
    find_all_result = pattern.findall(string)
    
    print('find all phone number result: ' + str(find_all_result)) 

        

if __name__ == '__main__':
    
    # create a regexp pattern to match a phone number
    phone_number_format = r'\d\d\d-\d\d\d\d\d\d\d\d'
    phone_number_pattern = re.compile(phone_number_format)
    
    # this is the phone number string that contain 3 phone number, but only the first 2 match above phone number pattern.
    phone_number_string = 'phone_number_1: 010-88888889;phone_number_2:012-89877987; phont_number_3: 0893-898998'

     
    regexp_search_function(phone_number_pattern, phone_number_string)
    
    regexp_find_all_function(phone_number_pattern, phone_number_string)
    
    # create a regexp pattern to match a phone number with group, please notice the parentheses in the pattern format string. 
    phone_number_format_use_group = r'(\d\d\d)-(\d\d\d\d\d\d\d\d)'
    phone_number_pattern = re.compile(phone_number_format_use_group)
    # above phone number pattern will return 
    regexp_find_all_function(phone_number_pattern, phone_number_string)

Below is above example execution result.

search phone number result: 010-88888889

find all phone number result: ['010-88888889', '012-89877987']

find all phone number result: [('010', '88888889'), ('012', '89877987')]

Reference

  1. What Is The Difference Between R & U Flag At Python String Beginning
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