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re.MatchObject.group() function in Python Regex

  • Difficulty Level : Easy
  • Last Updated : 27 May, 2021
Geek Week

re.MatchObject.group() method returns the complete matched subgroup by default or a tuple of matched subgroups depending on the number of arguments

Syntax: re.MatchObject.group([group])

Parameter:

  • group: (optional) group defaults to zero (meaning that it it will return the complete matched string). Return -1 if group exists but did not contribute to the match.

Return: Complete match by default else one or more matched subgroups depending on the arguments.

IndexError: If the group number passed as argument is negative or greater than the number of groups defined in the match pattern then an IndexError exception will be raised



AttributeError: If a matching pattern is not found then it raise AttributeError.

Consider the below example:

Example 1:

A program to print the username, company_name and domain from a emailID

Python3




import re
 
"""We create a re.MatchObject and store it in
   match_object variable
   the '()' parenthesis are used to define a
   specific group"""
 
match_object = re.match(r'(\w+)@(\w+)\.(\w+)', 'username@geekforgeeks.org')
 
""" w in above pattern stands for alphabetical character
    + is used to match a consecutive set of characters
    satisfying a given condition
    so w+ will match a consecutive set of alphabetical characters"""
 
# for entire match
print(match_object.group())
# also print(match_object.group(0)) can be used
 
# for the first parenthesized subgroup
print(match_object.group(1))
 
# for the second parenthesized subgroup
print(match_object.group(2))
 
# for the third parenthesized subgroup
print(match_object.group(3))
 
# for a tuple of all matched subgroups
print(match_object.group(1, 2, 3))

Output:

username@geekforgeeks.org
username
geekforgeeks
org
('username', 'geekforgeeks', 'org')

It’s time to understand the above program. We use a re.match() method to find a match in the given string(‘username@geekforgeeks.org‘) the ‘w‘ indicates that we are searching for an alphabetical character and the ‘+‘ indicates that we are searching for continuous alphabetical characters in the given string. Note the use of ‘()‘ the parenthesis is used to define different subgroups, in the above example, we have three subgroups in the match pattern. The result we get is a re.MatchObject which is stored in match_object.

Note: To know more about regex patterns refer Python regex 



Depending on the arguments passed the group method returns us different strings and also it returns a tuple of matched strings.

Example 2:

If we pass an invalid group number in the method argument then we will get an IndexError exception.

Python3




import re
 
"""We create a re.MatchObject and store it in
   match_object variable
   the '()' parenthesis are used to define a
   specific group"""
 
match_object = re.match(r'(\w+)@(\w+)\.(\w+)', 'username@geekforgeeks.org')
 
""" w in above pattern stands for alphabetical character
    + is used to match a consecutive set of characters
    satisfying a given condition
    so w+ will match a consecutive set of alphabetical characters"""
 
# Following line will raise IndexError exception
print(match_object.group(7))

Output:

Traceback (most recent call last):
  File "/home/8da42759204c98da7baa88422a4a74e0.py", line 17, in 
    print(match_object.group(7))
IndexError: no such group

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