[Python-Dev] int() and math.trunc don't accept objects that only define __index__
steve at pearwood.info
Thu Mar 14 22:45:42 EDT 2019
On Wed, Mar 13, 2019 at 03:21:31AM -0700, Rémi Lapeyre wrote:
> When __index__ is defined it means that there is a lossless conversion
> to int possible. In this case, this means a lossless conversion to
> float and complex is also possible
That's not correct:
py> n = 2**64 + 1
py> n == int(float(n))
Python floats (C doubles) can lose digits when converting from ints
over 2**53 or so.
> (with the exception of overflows
> but anyone doing float(var) should expect them).
I don't. I expect float(var) to overflow to infinity, if it is going to
overflow, and always forget that it can raise.
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
OverflowError: int too large to convert to float
This never fails to surprise me.
More information about the Python-Dev