Python - Convert Key-Values List to Flat Dictionary

Given a list of key-value pairs, the task is to convert it into a flat dictionary. For example:

Input: [("name", "Ak"), ("age", 25), ("city", "NYC")]
Output: {'name': 'Ak', 'age': 25, 'city': 'NYC'}

Below are multiple methods to convert a key-value list into a dictionary efficiently.

Using dict()

dict() constructor converts a list of key-value pairs into a dictionary by using each sublist's first element as a key and the second element as a value. This results in a flat dictionary where the key-value pairs are mapped accordingly.

a = [("name", "Emma"), ("age", 25), ("city", "New York")]
res = dict(a)
print(res)  

{'name': 'Emma', 'age': 25, 'city': 'New York'}

Using Dictionary Comprehension

Dictionary comprehension {key: value for key, value in a} iterates through the list a, unpacking each tuple into key and value. It then directly creates a dictionary by assigning the key to its corresponding value.

a = [("name", "Emma"), ("age", 25), ("city", "New York")]  
res = {key: value for key, value in a}
print(res)

{'name': 'Emma', 'age': 25, 'city': 'New York'}

Using a Loop

For loop iterates through each tuple in the list 'a', extracting the key and value, and then adds them to a dictionary. The dictionary is built incrementally by mapping each key to its corresponding value.

a = [("name", "Emma"), ("age", 25), ("city", "New York")]
b = {}
for key, value in a:
    b[key] = value

print(b)

{'name': 'Emma', 'age': 25, 'city': 'New York'}

Explanation:

• for loop iterates through each tuple in the list a, unpacking it into key and value.
• In each iteration, the key is used to assign the value to the dictionary b, effectively constructing the dictionary

Using zip()

zip() function pairs the keys from a with corresponding values from b, creating key-value pairs. These pairs are then converted into a dictionary using dict().

a = ["name", "age", "city"]  # List of keys
b = ["Emma", 25, "New York"]  # List of values
res = dict(zip(a, b))
print(res) 

{'name': 'Emma', 'age': 25, 'city': 'New York'}

Explanation:

• zip(keys, values) creates an iterator of key-value tuples.
• dict() converts these tuples into a dictionary.