What the Comprehension Can See

class Deck:
    ranks = [2, 3, 4]
    doubled = [r * 2 for r in ranks]

class Deck2:
    multiplier = 2
    ranks = [2, 3, 4]
    doubled = [r * multiplier for r in ranks]

One of these two class bodies raises NameError when the module is loaded. Which, and why?

Both raise NameError, because list comprehensions can never reference any name defined earlier in the same class body.

Deck2 raises NameError on multiplier: it is only referenced inside the comprehension's own scope, which cannot see class-body names, while Deck.ranks works because it is the outermost for's iterable, evaluated eagerly in the class body itself before that inner scope exists.

Deck raises NameError on ranks, since a comprehension's own scope can never see any name from its enclosing class body, including the iterable it loops over.

Neither raises: comprehensions always run inside the enclosing class body's own namespace, so both ranks and multiplier resolve normally.