Group By Matching Second Tuple Value in List of Tuples in Python

In this tutorial, we are going to write a program that groups all the tuples from a list that have same element as a second element. Let's see an example to understand it clearly.

Input

[('Python', 'tutorialspoints'), ('Management', 'other'), ('Django', 'tutorialspoints'), ('React',
'tutorialspoints'), ('Social', 'other'), ('Business', 'other')]

Output

{'tutorialspoint': [('Python', 'tutorialspoints'), ('Django', 'tutorialspoints'), ('React', 'tutorialspoints')],
'other’: [('Management', 'other'), ('Social', 'other'), ('Business', 'other')]}

We have to group the tuples from the list. Let's see the steps to solve the problem.

• Initiate a list with required tuples.
• Create an empty dictionary.
• Iterate through the list of tuples.
  • Check if the second element of the tuple is already present in the dictionary or not.
  • If it already present, then append the current tuple to its list.
  • Else initialize the key with a list with the current tuple.
• At the end, you will get a dictionary with the required modifications.

Example

# initializing the list with tuples
tuples = [('Python', 'tutorialspoints'), ('Management', 'other'), ('Django', 't
ialspoints'), ('React', 'tutorialspoints'), ('Social', 'other'), ('Business', 'othe
r')]
# empty dict
result = {}
# iterating over the list of tuples
for tup in tuples:
   # checking the tuple element in the dict
   if tup[1] in result:
      # add the current tuple to dict
      result[tup[1]].append(tup)
   else:
      # initiate the key with list
      result[tup[1]] = [tup]
# priting the result
print(result)

Output

If you run the above code, then you will get the following result.

{'tutorialspoints': [('Python', 'tutorialspoints'), ('Django', 'tutorialspoints
('React', 'tutorialspoints')], 'other': [('Management', 'other'), ('Social', 'other
'), ('Business', 'other')]}

We skip the if condition in the above program using defaultdict. Let's solve it using the defaultdict.

Example

# importing defaultdict from collections
from collections import defaultdict
# initializing the list with tuples
tuples = [('Python', 'tutorialspoints'), ('Management', 'other'), ('Django', 't
ialspoints'), ('React', 'tutorialspoints'), ('Social', 'other'), ('Business', 'othe
r')]
# empty dict with defaultdict
result = defaultdict(list)
# iterating over the list of tuples
for tup in tuples:
   result[tup[1]].append(tup)
   # priting the result
   print(dict(result))

Output

If you run the above code, then you will get the following result.

{'tutorialspoints': [('Python', 'tutorialspoints'), ('Django', 'tutorialspoints
('React', 'tutorialspoints')], 'other': [('Management', 'other'), ('Social', 'other
'), ('Business', 'other')]}

Conclusion

You can solve it different in ways as you like. We have seen two ways here. If you have any doubts in the tutorial, mention them in the comment section.