Very simple question, but I can't find the answer to it. My IDE vs code (pylance) give me the warning/hint for a being possibly unbound. Why is this? How do I fix it?
def f():
for i in range(4):
a = 1
print(a)
return a
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Gang
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Your code is invalid, enumerate takes iterable as input you can't pass int may be you need a ``range``. – sushanth Aug 13 '20 at 04:57
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`enumerate(4)`? That's not going to work. The warning means that you should take into account that a `for` loop can run 0 times and `a` would be undefined. – Klaus D. Aug 13 '20 at 05:00
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1@Sushanth, @Klaus I have changed it to `range` – Gang Aug 13 '20 at 05:00
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2You can add a=None before the for loop – sam Aug 13 '20 at 05:43
1 Answers
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Because range(4) might be something empty (if you overwrite the built-in range), in which case the loop body will never run and a will not get assigned. Which is a problem when it's supposed to get returned.
Maybe you can tell your IDE to ignore this and not show the warning. Or assign some meaningful default to a before the loop.
superb rain
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6If you assign e.g. `None` before the loop, you can `assert is not None` afterwards to get the inferred type from `int | None` back to `int` and still catch errors early where the loop indeed didn't execute (instead of returning the `None` default value). – xuiqzy Jan 30 '21 at 12:16