double_evens.py

def double_evens1(inp):
    for item in inp:
        if not item % 2:
            yield item
        yield item
        
def double_evens2(inp):
    for item in inp:
        if not item % 2:
            yield item
            yield item
        else:
            yield item
            

for size in [10, 100, 1000, 10000, 100000]:
    mylist = list(range(size))

    %timeit list(double_evens1(mylist))
    %timeit list(double_evens2(mylist))
    
#9.76 µs ± 330 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
#9.24 µs ± 25.1 ns per loop (mean ± std. dev. of 7 runs, 100000 loops each)
#59.3 µs ± 65.9 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
#59.5 µs ± 222 ns per loop (mean ± std. dev. of 7 runs, 10000 loops each)
#536 µs ± 28.9 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
#637 µs ± 87.6 µs per loop (mean ± std. dev. of 7 runs, 1000 loops each)
#5.22 ms ± 142 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
#5.2 ms ± 148 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
#54.5 ms ± 1.96 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
#53.6 ms ± 441 µs per loop (mean ± std. dev. of 7 runs, 10 loops each)