Generator Pipeline

Build a generator that lazily filters and maps an iterable of numbers.

generators lazy-evaluation filter map

Write a generator function named `pipeline` that takes a single argument `numbers`, which is an iterable of integers.

When iterated, `pipeline(numbers)` must yield, in the same order they appear, the squares of only the even numbers in the input. The generator must be lazy: it should not process the entire input upfront, and it should work with any iterable (including infinite iterables like `itertools.count()`).

You must not use `yield from`, list comprehensions, or generator expressions. Only plain `yield` statements and loops are allowed.

Define the function exactly as:
```python
def pipeline(numbers):
    ...
```

Examples:
- pipeline([1, 2, 3, 4]) yields 4, 16.
- pipeline([]) yields nothing.
- pipeline([5, 7, 9]) yields nothing.
- pipeline([2]) yields 4.

Constraints

Input numbers is an iterable of integers. The function returns a generator object. Each element can be any integer (positive, negative, or zero). There is no limit on the length of the iterable, but the generator must be lazy.

Example

>>> gen = pipeline([1, 2, 3, 4])
>>> list(gen)
[4, 16]
>>> list(pipeline([]))
[]
>>> list(pipeline([5, 7, 9]))
[]
>>> list(pipeline([2]))
[4]

8 points ~12 min

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Hints

Iterate over the input with a for loop.

Use the modulus operator `%` to test evenness.

Yield the square `n * n` only for even numbers.

Remember: generators are lazy, so you can just yield as you go.

Test Results

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