Convert a List to Dictionary Python

We are given a list we need to convert the list in dictionary. For example, we are given a list a=[10,20,30] we need to convert the list in dictionary so that the output should be a dictionary like {0: 10, 1: 20, 2: 30}. We can use methods like enumerate, zip to convert a list to dictionary in python.

Using enumerate()

Using enumerate() allows us to iterate over a list with an index which can be used as keys to map elements directly to a dictionary.

# List of values
a = [10, 20, 30]

# Convert to dictionary with index as key and value as value
b = {index: value for index, value in enumerate(a)}
print(b)

{0: 10, 1: 20, 2: 30}

Explanation:

• enumerate() function generates pairs of indices and values, which are directly used in a dictionary comprehension.
• Dictionary comprehension creates a key-value pair for each index and its corresponding list element.

Grouping Elements into Key-Value Pairs

Grouping elements into key-value pairs involves pairing consecutive elements in a list where the first becomes key and next becomes the value.

a = ["a", 1, "b", 2, "c", 3]

# Create dictionary by pairing elements, using every second element as value
result = {a[i]: a[i + 1] for i in range(0, len(a), 2)}
print(result)  

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

Explanation:

• List a contains alternating keys and values, where odd-indexed elements are keys and even-indexed elements are their corresponding values.
• Dictionary comprehension iterates over the list with a step of 2, pairing each key with its following value to form a dictionary.

Using zip()

Using zip() allows pairing two lists, one for keys and the other for values, to create a dictionary. This method is efficient for custom key-value mappings when you have separate lists for each.

a = ["apple", "banana", "cherry"]

# Create dictionary where each fruit is a key, and its length is the value
b = {value: len(value) for value in a}

print(b)  

{'apple': 5, 'banana': 6, 'cherry': 6}

Explanation:

• List a contains fruit names, which are used as keys in the dictionary.
• Dictionary comprehension assigns the length of each fruit name as the corresponding value for each key.