Python - Convert key-values list to flat dictionary

We are given a list that contains tuples with the pairs of key and values we need to convert that list into a flat dictionary. For example a = [("name", "Ak"), ("age", 25), ("city", "NYC")] is a list we need to convert it to dictionary so that output should be a flat dictionary {'name': 'Ak', 'age': 25, 'city': 'NYC'}. For this we can use multiple method like dict, loop with various approach.

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", "Alice"), ("age", 25), ("city", "New York")]  # List of key-value pairs as tuples

# Convert the list of key-value pairs into a flat dictionary using the dict() constructor
res = dict(a)

print(res)  

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

Explanation:

• List a contains tuples, where each tuple consists of a key and its corresponding value.
• dict() constructor converts the list of key-value pairs into a flat dictionary, mapping each key to its value.

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", "Alice"), ("age", 25), ("city", "New York")]

b = {}
for key, value in a:
    b[key] = value

print(b)

{'name': 'Alice', '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 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", "Alice"), ("age", 25), ("city", "New York")]  # List of key-value pairs as tuples

# Use dictionary comprehension to create a dictionary by unpacking each tuple into key and value
res = {key: value for key, value in a}

print(res)

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

Explanation:

• Dictionary comprehension iterates over the list a, unpacking each tuple into key and value.
• Each key is mapped to its corresponding value, and the comprehension directly constructs the dictionary res.

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 = ["Alice", 25, "New York"]  # List of values

# Use zip to pair each key from 'a' with the corresponding value from 'b', then convert the pairs to a dictionary
res = dict(zip(a, b))

print(res) 

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

Explanation:

• zip() function combines elements from the lists a (keys) and b (values) into key-value pairs.
• dict() constructor then converts the paired elements into a dictionary, mapping each key to its corresponding value.

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Article Tags :

• Python
• Python Programs
• Python dictionary-programs

Practice Tags :

• python