2.0 KiB

Raw Permalink Blame History

Comprehensions

Basic comprehensions

# revealed: int
[reveal_type(x) for x in range(3)]

class Row:
    def __next__(self) -> range:
        return range(3)

class Table:
    def __iter__(self) -> Row:
        return Row()

# revealed: tuple[int, range]
[reveal_type((cell, row)) for row in Table() for cell in row]

# revealed: int
{reveal_type(x): 0 for x in range(3)}

# revealed: int
{0: reveal_type(x) for x in range(3)}

Nested comprehension

# revealed: tuple[int, int]
[[reveal_type((x, y)) for x in range(3)] for y in range(3)]

Comprehension referencing outer comprehension

class Row:
    def __next__(self) -> range:
        return range(3)

class Table:
    def __iter__(self) -> Row:
        return Row()

# revealed: tuple[int, range]
[[reveal_type((cell, row)) for cell in row] for row in Table()]

Comprehension with unbound iterable

Iterating over an unbound iterable yields Unknown:

# error: [unresolved-reference] "Name `x` used when not defined"
# revealed: Unknown
[reveal_type(z) for z in x]

# error: [not-iterable] "Object of type `int` is not iterable"
# revealed: tuple[int, Unknown]
[reveal_type((x, z)) for x in range(3) for z in x]

Starred expressions

Starred expressions must be iterable

class NotIterable: ...

# This is fine:
x = [*range(3)]

# error: [not-iterable] "Object of type `NotIterable` is not iterable"
y = [*NotIterable()]

Async comprehensions

Basic

class AsyncIterator:
    async def __anext__(self) -> int:
        return 42

class AsyncIterable:
    def __aiter__(self) -> AsyncIterator:
        return AsyncIterator()

async def _():
    # revealed: int
    [reveal_type(x) async for x in AsyncIterable()]

Invalid async comprehension

This tests that we understand that async comprehensions do not work according to the synchronous iteration protocol

async def _():
    # error: [not-iterable] "Object of type `range` is not async-iterable"
    # revealed: Unknown
    [reveal_type(x) async for x in range(3)]

2.0 KiB Raw Permalink Blame History