Get all Tuple Keys from Dictionary - Python

In Python, dictionaries can have tuples as keys which is useful when we need to store grouped values as a single key. Suppose we have a dictionary where the keys are tuples and we need to extract all the individual elements from these tuple keys into a list. For example, consider the dictionary : d = {(5, 6): 'gfg', (9, 10): 'best', (1, 2, 8): 'is'} here the keys are (5, 6), (9, 10), and (1, 2, 8) and our task is to retrieve all the elements from these tuples into a single list: [5, 6, 9, 10, 1, 2, 8].

Using dictionary comprehension and chain.from_iterable()

In this method we can use itertools.chain.from_iterable() to flatten the tuple keys directly into a list.

from itertools import chain

d = {(5, 6): 'gfg', (9, 10): 'best', (1, 2, 8): 'is'}

res = list(chain.from_iterable(d.keys()))

print(res) 

[5, 6, 9, 10, 1, 2, 8]

Explanation:

• d.keys() gives us all tuple keys and chain.from_iterable(d.keys()) flattens the tuple keys into a single sequence.
• list() converts the sequence into a list.

Using a generator expression and chain()

This method offers a memory-efficient way of flattening the tuple keys as the generator expression generates the keys on the fly and chain() combines them into a single list without the need to create multiple intermediate lists.

from itertools import chain

d = {(5, 6): 'gfg', (9, 10): 'best', (1, 2, 8): 'is'}

res = list(chain(*(key for key in d)))

print(res)

[5, 6, 9, 10, 1, 2, 8]

Explanation:

• We use a generator expression (key for key in d) to iterate over the tuple keys and the * operator unpacks the tuples before passing them to chain() which flattens them.
• list() converts the result into a list.

Using a loop and extend()

This method is simple and intuitive as it uses a loop to go through each tuple key in the dictionary and extend() function to add the elements of each tuple to a list . while it’s easy to understand it involves more overhead due to the multiple function calls within the loop.

from itertools import chain

d = {(5, 6): 'gfg', (9, 10): 'best', (1, 2, 8): 'is'}

res = []
for key in d:
    res.extend(key)

print(res)

[5, 6, 9, 10, 1, 2, 8]

Explanation:

• We initialize an empty list res and iterate through each tuple key in the dictionary.
• Using extend(), we add all elements of each tuple to res.

Using sum() with list unpacking

This method is straightforward and simple to understand as it uses sum() to combine the elements of the tuples into one list but it’s less efficient for large datasets because it repeatedly creates new lists for each tuple.

d = {(5, 6): 'gfg', (9, 10): 'best', (1, 2, 8): 'is'}

res = sum((list(key) for key in d), [])

print(res)

[5, 6, 9, 10, 1, 2, 8]

Explanation:

• We use a generator expression (list(key) for key in d) to convert each tuple key into a list.
• sum() then adds all these lists together and by providing an initial empty list [] we concatenate all the lists into one.