Dictionary Comprehensions

Dictionary comprehensions allow us to create new dictionaries by specifying both a key and a value expression, separated by a colon :.

Mapping and Transforming Data​

We use dictionary comprehensions to transform existing dictionaries or build new ones from other iterables.

tea_price_inr = {"Masala Chai": 10, "Green Chai": 50}

# Convert prices from INR to USD (assuming 1 USD = 80 INR)
tea_dollar = {key: val / 80 for key, val in tea_price_inr.items()}

print(tea_dollar)

Output:

{'Masala Chai': 0.125, 'Green Chai': 0.625}

Creating Dicts from Iterables​

We can also create dictionaries from lists using logic to determine keys or values.

names = ["Alice", "Bob", "Charlie"]

# Create a mapping of Name -> Length
name_lengths = {name: len(name) for name in names}
print(name_lengths)

Output:

{'Alice': 5, 'Bob': 3, 'Charlie': 7}