PyCharm warns "Expected type 'int', got 'float'" for random.randint, but code still runs sometimes

Question

PyCharm (Python version 3.11.3 on Windows) is flagging Expected type 'int', got 'float' instead where I use random.randint(x/y, 10) (where x/y will be, say, 5.0), which makes sense. However the code still runs.

Someone else using a different IDE tried to run the code and TypeError prevented the code from running. I don't know what system/version that was on, but it doesn't make sense to me.

For minimal viable program:

import random

x = 10
y = 2

print(random.randint(x/y, 10)

Why is there a discrepancy between the PyCharm warning and the runtime errors, and why is it not consistent across systems?

Answer 1

The warnings/errors that PyCharm gives are the result of static analysis based on type hints and can in principle be different from the runtime behaviour.

In the case of random.randint, prior to Python 3.12, it accepted integer-value float arguments and converted them to int implicitly.

Since Python 3.12, float arguments are no longer allowed at all, see https://docs.python.org/3/library/random.html#random.randrange (randint delegates to randrange).

So, two things could have caused a TypeError:

• The Python version was ≥3.12.
• x/y was not an exact integer value (e.g. 0.3/0.1 is mathematically 3 but in floating-point arithmetic slightly smaller than 3).