Python – Join Tuples if similar initial element

Sometimes, while working with Python tuples, we can have a problem in which we need to perform concatenation of records from the similarity of initial element. This problem can have applications in data domains such as Data Science. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [(5, 6), (5, 7), (5, 8), (6, 10), (7, 13)]
Output : [(5, 6, 7, 8), (6, 10), (7, 13)]

Input : test_list = [(5, 6), (6, 7), (6, 8), (6, 10), (7, 13)]
Output : [(5, 6), (6, 7, 8, 10), (7, 13)]

Method #1 : Using loop
This is brute way in which this task can be done. In this, we create new tuple, if we find no occurrence of similar tuple values previously. Slicing is used to add rest of elements to created tuple.

# Python3 code to demonstrate working of
# Join Tuples if similar initial element
# Using loop

# initializing list
test_list = [(5, 6), (5, 7), (6, 8), (6, 10), (7, 13)]

# printing original list
print("The original list is : " + str(test_list))

# Join Tuples if similar initial element
# Using loop
res = []
for sub in test_list:										
	if res and res[-1][0] == sub[0]:			
		res[-1].extend(sub[1:])						
	else:
		res.append([ele for ele in sub])	
res = list(map(tuple, res))

# printing result
print("The extracted elements : " + str(res))

Output :

The original list is : [(5, 6), (5, 7), (6, 8), (6, 10), (7, 13)]
The extracted elements : [(5, 6, 7), (6, 8, 10), (7, 13)]

Method #2 : Using defaultdict() + loop
The combination of above functions can be used to solve this problem. The advantages it offers from above method are, that it reduces one check of initializing new key, and also works well even if similar elements are not consecutive.

# Python3 code to demonstrate working of
# Join Tuples if similar initial element
# Using defaultdict() + loop
from collections import defaultdict

# initializing list
test_list = [(5, 6), (5, 7), (6, 8), (6, 10), (7, 13)]

# printing original list
print("The original list is : " + str(test_list))

# Join Tuples if similar initial element
# Using defaultdict() + loop
mapp = defaultdict(list)
for key, val in test_list:
	mapp[key].append(val)
res = [(key, *val) for key, val in mapp.items()]

# printing result
print("The extracted elements : " + str(res))

Output :

The original list is : [(5, 6), (5, 7), (6, 8), (6, 10), (7, 13)]
The extracted elements : [(5, 6, 7), (6, 8, 10), (7, 13)]