Dictionary Comprehensions

squares = {n: n ** 2 for n in range(6)}
print(squares)

parts_by_mass = {"booster": 25000, "second stage": 4500, "fairing": 1900}
heavy_parts = {name: mass for name, mass in parts_by_mass.items() if mass > 2000}
print(heavy_parts)

{0: 0, 1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
{'booster': 25000, 'second stage': 4500}