[Python-Dev] Symmetry arguments for API expansion (original) (raw)

Serhiy Storchaka storchaka at gmail.com
Mon Mar 12 15:53:51 EDT 2018

12.03.18 21:15, Guido van Rossum пише:

There's a reason why adding this to int feels right to me. In mypy we treat int as a subtype of float, even though technically it isn't a subclass.. The absence of an isinteger() method on int means that this code has a bug that mypy doesn't catch:

def f(x: float): if x.isinteger(): "do something" else: "do something else"

What is the real use case of float.is_integer()?

I searched on GitHub and found only misuses of it like (x/5).is_integer() (x % 5 == 0 would be more correct and clear) or (x**0.5).is_integer() (returns wrong result for large ints and some floats) in short examples. Some of these snippets look like book examples, and they propagate bad practices (like "if a.is_integer() == True:").

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