Generator function with yield

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Accepted Answer

A generator function uses yield instead of return. Calling count_up(3) does not execute the body - it returns a generator object. Each call to next() resumes the function from where it last yielded. First next(): runs until yield 0, pauses, returns 0. Second next(): resumes, runs until yield 1, returns 1. The function body is frozen between calls, which is what makes generators memory-efficient.