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r/learnpython 23-01-2018
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def none_slice_gabriel(lst, start, stop): | |
i = start | |
while i < 0 and i < stop: | |
yield None | |
i += 1 | |
while i < len(lst) and i < stop: | |
yield lst[i] | |
i += 1 | |
while i < stop: | |
yield None | |
i += 1 | |
def none_slice_elbiot(mylist, start, stop): | |
length = len(mylist) | |
if stop < start: | |
raise ValueError('{} is not less than {}'.format(start, stop)) | |
elif (stop < 0) or (start > length-1): | |
return [None] * (stop - start) | |
else: | |
part1 = [None] * (0 - min(start, 0)) | |
part2 = mylist[max(start, 0):stop] # negative start causes empty | |
part3 = [None] * max(0, stop-length) | |
return part1 + part2 + part3 | |
def main(): | |
test_cases = [ | |
(-5, -5, []), | |
(-5, 0, [None] * 5), | |
(-2, 2, [None, None, 0, 1]), | |
(0, 0, []), | |
(0, 5, list(range(5))), | |
(3, 7, list(range(3, 7))), | |
(9, 11, [9, None]), | |
(10, 11, [None]), | |
(11, 11, []) | |
] | |
mylist = [i for i in range(23) if i % 2 == 0] | |
for start, stop, _ in test_cases: | |
x = list(none_slice_gabriel(mylist, start, stop)) | |
y = none_slice_elbiot(mylist, start, stop) | |
assert x == y | |
if __name__ == '__main__': | |
main() |
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