re.MatchObject.group() function in Python Regex - GeeksforGeeks

27 May, 2021
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 matchprint(match_object.group())# also print(match_object.group(0)) can be used # for the first parenthesized subgroupprint(match_object.group(1)) # for the second parenthesized subgroupprint(match_object.group(2)) # for the third parenthesized subgroupprint(match_object.group(3)) # for a tuple of all matched subgroupsprint(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 exceptionprint(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
simranarora5sos
python-regex
Python
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