Create a List using Custom Key-Value Pair of a Dictionary – Python

Last Updated : 28 Jan, 2025

The task of creating a list using custom key-value pairs from a dictionary involves extracting the dictionary’s keys and values and organizing them into a list of tuples. This allows for the flexibility of representing data in a sequence that maintains the relationship between keys and values.

For example, if we have a dictionary like {‘a’: 1, ‘b’: 2, ‘c’: 3}, the goal is to convert it into a list like [(‘a’, 1), (‘b’, 2), (‘c’, 3)].

Using zip()

zip() combines two or more iterables into tuples. To create a list from a dictionary’s key-value pairs, we can use zip() to combine the keys and values separately and then create the desired list. Although the zip() is useful in certain scenarios, it’s less common for creating lists of key-value pairs from a dictionary directly.

Python

d = {'a': 1, 'b': 2, 'c': 3, 'd': 4}

key = d.keys()
val = d.values()
res = list(zip(key, val))
print(res)

Output

[('a', 1), ('b', 2), ('c', 3), ('d', 4)]

Explanation:

d.keys() retrieves the keys from the dictionary d .
d.values() retrieves the values from the dictionary d .
zip() combines the two iterables into pairs. It pairs the first key with the first value, the second key with the second value and so on.

Table of Content

Using map()
Using list comprehension
Using loop

Using map()

map() allows us to apply a transformation to each element in an iterable. While it’s more commonly used with lists, we can combine map() with a lambda function to extract and create custom key-value pairs from a dictionary.

Python

d = {'a': 1, 'b': 2, 'c': 3, 'd': 4}

res = list(map(lambda item: (item[0], item[1]), d.items()))
print(res)

Output

[('a', 1), ('b', 2), ('c', 3), ('d', 4)]

Explanation:

d.items() returns key-value pairs as tuples: (‘a’, 1), (‘b’, 2), (‘c’, 3), (‘d’, 4).
map() applies the lambda function to each item, extracting the key and value as a tuple.
list() converts the result to a list.

Using list comprehension

List comprehension is a efficient way to construct lists. It’s particularly useful when we need to process or transform items from an iterable. Using list comprehension, we can efficiently extract custom key-value pairs and create the desired list:

Python

d= {'a': 1, 'b': 2, 'c': 3, 'd': 4}

res = [(key, val) for key, val in d.items()]
print(res)

Output

[('a', 1), ('b', 2), ('c', 3), ('d', 4)]

Explanation: List Comprehension iterates over the dictionary’s key-value pairs and creates a list of tuples.

Using loop

for loop is one of the most straightforward and flexible ways to extract key-value pairs from a dictionary. It allows us to iterate over the dictionary’s items explicitly, providing full control over the process of extracting and transforming data.

Python

d= {'a': 1, 'b': 2, 'c': 3, 'd': 4}

res= [] # initialized an empty list

for key, val in d.items():
    res.append((key, val))
print(res)

Output

[('a', 1), ('b', 2), ('c', 3), ('d', 4)]

Explanation:

for loop iterates over each key-value pair in the dictionary d .
.items() returns a sequence of tuples, each containing a key and its associated value.