Python – Tuple to Dictionary Summation conversion

Sometimes, while working with Python tuples, we can have a problem in which we can have data points in tuples, and we need to convert them to dictionary after performing summation of similar keys. This kind of operation can also be extended to max, min or product. This can occur in data domains. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [(5, 8), (5, 6), (5, 2), (5, 8), (5, 10)] 
Output : {5: 34}

Input : test_list = [(5, 8), (9, 6)] 
Output : {5: 8, 9: 6}

Method #1 : Using loop + defaultdict() The combination of above functions can be used to solve this problem. In this, we initialize the counter dictionary with integers using defaultdict() and loop is used to iterate for all data points. 

Python3

# Python3 code to demonstrate working of
# Tuple to Dictionary Summation conversion
# Using defaultdict() + loop
from collections import defaultdict

# initializing list
test_list = [(7, 8), (5, 6), (7, 2), (6, 8), (5, 10)]

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

# Tuple to Dictionary Summation conversion
# Using defaultdict() + loop
res = defaultdict(int)
for sub in test_list:
    res[sub[0]] += sub[1]

# printing result
print("The summation tuple dictionary : " + str(dict(res)))

Output : 

The original list is : [(7, 8), (5, 6), (7, 2), (6, 8), (5, 10)]
The summation tuple dictionary : {7: 10, 5: 16, 6: 8}

Time complexity: O(n), where n is the number of elements in the input list.
Auxiliary space: O(n), where n is the number of elements in the input list. 

Method #2 : Using dictionary comprehension + sum() + groupby() The combination of above functions can be used to solve this problem. In this, we perform the task of summation using sum(), groupby() is used to group similar elements for further computations. 

Python3

# Python3 code to demonstrate working of
# Tuple to Dictionary Summation conversion
# Using dictionary comprehension + sum() + groupby()
from itertools import groupby

# initializing list
test_list = [(7, 8), (5, 6), (7, 2), (6, 8), (5, 10)]

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

# Tuple to Dictionary Summation conversion
# Using dictionary comprehension + sum() + groupby()
fnc = lambda ele: ele[0]
res = {key: sum(sub[1] for sub in val) for key, val in groupby(
                       sorted(test_list, key = fnc), key = fnc)}

# printing result
print("The summation tuple dictionary : " + str(res))

Output : 

The original list is : [(7, 8), (5, 6), (7, 2), (6, 8), (5, 10)]
The summation tuple dictionary : {7: 10, 5: 16, 6: 8}

Time Complexity: O(n*n), where n is the number of elements in the list “test_list”.
Auxiliary Space: O(n), where n is the number of elements in the list “test_list”.

Method 3 – Using defaultdict and a for loop

This method uses defaultdict(int) to create a dictionary where the default value for any key is 0. It then loops through each tuple in test_list and adds the second element of the tuple to the value of the corresponding key in the dictionary. Finally, the defaultdict is converted to a regular dictionary using the dict() function.

Python3

from collections import defaultdict

# initializing list
test_list = [(7, 8), (5, 6), (7, 2), (6, 8), (5, 10)]

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

# Tuple to Dictionary Summation conversion
# Using defaultdict and for loop
res = defaultdict(int)
for tpl in test_list:
    res[tpl[0]] += tpl[1]

# converting defaultdict to dictionary
res = dict(res)

# printing result
print("The summation tuple dictionary : " + str(res))

Output

The original list is : [(7, 8), (5, 6), (7, 2), (6, 8), (5, 10)]
The summation tuple dictionary : {7: 10, 5: 16, 6: 8}

Time complexity: The time complexity of this implementation is O(n), where n is the length of the input list. 
Auxiliary space: The auxiliary space used by this implementation is O(m), where m is the number of distinct keys in the input list.

Method#4: Using Recursive method.

Algorithm:

1. If the input list is empty, return an empty dictionary.
2. Extract the first tuple from the input list and recursively process the rest of the list.
3. If the key (first element of the tuple) is already present in the dictionary returned by the recursive call, add the value (second element of the tuple) to its existing value.
4. If the key is not present in the dictionary, add it with the corresponding value.
5. Return the updated dictionary.

Python3

def tuple_to_dict_summation(test_list):
    # Base case: if list is empty, return empty dictionary
    if not test_list:
        return {}

    # Recursive case: extract first tuple and recursively process the rest of the list
    first_tuple = test_list[0]
    rest_of_list = test_list[1:]
    sub_dict = tuple_to_dict_summation(rest_of_list)

    # Update dictionary with values from current tuple
    if first_tuple[0] in sub_dict:
        sub_dict[first_tuple[0]] += first_tuple[1]
    else:
        sub_dict[first_tuple[0]] = first_tuple[1]

    return sub_dict
test_list = [(7, 8), (5, 6), (7, 2), (6, 8), (5, 10)]

res = tuple_to_dict_summation(test_list)
print("The summation tuple dictionary : " + str(res))

Output

The summation tuple dictionary : {5: 16, 6: 8, 7: 10}

Time complexity:

The function processes each tuple in the list exactly once, so the time complexity is O(n), where n is the length of the input list.

Auxiliary Space:

The function uses a recursive approach, so the space complexity is O(n) due to the recursive call stack, where n is the length of the input list. However, the space complexity of the dictionary created is also O(n) as each tuple creates one key-value pair in the dictionary. So, the overall space complexity is O(n).