Raymond Hettinger added the comment:
> the functions are so simple and self-explanatory
> that API-complexity does not really increase.
It increases complexity because it will show-up everywhere including places
where it makes little sense.
One place is int objects where its meaning and purpose will seem arcane to most
Python programmers. For int objects, this is just total waste.
With the fractions module, the method is also unnecessary because integral
fractions all have a denominator of 1.
With the decimal module, we were careful not to grow the API beyond what was in
the spec or what was necessary to integrate it into Python (i.e. the usual
magic methods). I think that was a good decision and would like to keep it
that way.
In general, the need for this method is almost nil (it would be a very, very
rare Python programmer who would ever need this, and those that might what it
are perfectly capable of writing a short function to handle their own
requirements). In the OPs case, the motivation isn't inability to determine
whether something is integral, it is more a desire for the test to be
polymorphic with other types where the methods do not add any real value.
The OPs notion of "absurd" behavior implies a rule that all float methods
should be available for ints. That would suggest the is_integer, hex, fromhex,
and as_integer_ratio would all need to propagate to the other types as well. I
don't think we should start sliding down that slope.
Another thought is that future updates to the decimal spec could make
conflicting choices about what Decimal.is_integral() would return for
Decimal('Infinity'). There could be a case to be made for true, for false, for
NaN, or for setting one or more of the signal flags or traps.
I'm glad that the OP separated out the request for Decimal given that his
actual use cases involve everything except Decimal. The decimal class is
intentionally not registered a Real (only as a Number) because it isn't
interoperable with binary floats; hence, there has been no need to copy all the
float methods into Decimal.
AFAICT, this comes down to whether to push a float method into other types
where we otherwise wouldn't do it, just to save the OP from one-line function:
is_integral = lambda x: isinstance(x, int) or isinstance(x, Fraction) and
x.denominator == 1 or isinstance(x, float) and x.is_integer()
----------
nosy: +tim.peters
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<http://bugs.python.org/issue26680>
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