Python - Mapping Key Values to Dictionary

We are given two list and we need to map key to values of another list so that it becomes dictionary. For example, we are given two list k = ['a', 'b', 'c'] and v = [1, 2, 3] we need to map the keys of list k to the values of list v so that the resultant output should be {'a': 1, 'b': 2, 'c': 3}.

Using zip()

zip() function pairs elements from two lists allowing us to create a dictionary using dict(zip(keys, values)) where each key gets mapped to its corresponding value.

k = ['a', 'b', 'c']
v = [1, 2, 3]

d = dict(zip(k, v))
print(d)

{'a': 1, 'b': 2, 'c': 3}

Explanation:

• zip(k, v) function pairs elements from lists k and v into tuples and dict() converts these tuples into key-value pairs in dictionary d.
• Resulting dictionary d is {'a': 1, 'b': 2, 'c': 3}, where each key from k is mapped to its corresponding value in v.

Using Dictionary Comprehension

Dictionary comprehension iterates through the indices of key list and maps each key to its corresponding value from value list.

k = ['a', 'b', 'c']
v = [1, 2, 3]

d = {k[i]: v[i] for i in range(len(k))}
print(d)

{'a': 1, 'b': 2, 'c': 3}

Explanation:

• This dictionary comprehension iterates over indices of the k list and assigns each key from k to its corresponding value from v using k[i]: v[i].
• It ensures that mapping is created efficiently without requiring external functions making it a straightforward approach when both lists have same length.

Using dict.fromkeys()

dict.fromkeys(k, v) creates a dictionary where all keys in k are mapped to the same single value v, not individual values from list. It is useful when assigning a default value to multiple keys.

k = ['a', 'b', 'c']
d = 0

d = dict.fromkeys(k, d)
print(d)

{'a': 0, 'b': 0, 'c': 0}

Explanation: dict.fromkeys(k, d) creates a dictionary where each key from the list k is assigned the same value d (which is 0 in this case).

Using map() and dict()

zip(k, v) function pairs corresponding elements from the key and value lists, which map() processes into key-value tuples dict() function then converts these tuples into a dictionary effectively mapping keys to values.

k = ['a', 'b', 'c']
v = [1, 2, 3]

d = dict(map(lambda k, v: (k, v), k, v))
print(d)

{'a': 1, 'b': 2, 'c': 3}

Explanation:

• map() function pairs each key in k with its corresponding value in v using a lambda function.
• dict() function then converts the mapped pairs into a dictionary.

Related Article:

• zip()
• dictionary
• Dictionary comprehension