bpo-26680: Incorporate is_integer in all built-in and standard library numeric types (GH-6121)
* bpo-26680: Adds support for int.is_integer() for compatibility with float.is_integer().
The int.is_integer() method always returns True.
* bpo-26680: Adds a test to ensure that False.is_integer() and True.is_integer() are always True.
* bpo-26680: Adds Real.is_integer() with a trivial implementation using conversion to int.
This default implementation is intended to reduce the workload for subclass
implementers. It is not robust in the presence of infinities or NaNs and
may have suboptimal performance for other types.
* bpo-26680: Adds Rational.is_integer which returns True if the denominator is one.
This implementation assumes the Rational is represented in it's
lowest form, as required by the class docstring.
* bpo-26680: Adds Integral.is_integer which always returns True.
* bpo-26680: Adds tests for Fraction.is_integer called as an instance method.
The tests for the Rational abstract base class use an unbound
method to sidestep the inability to directly instantiate Rational.
These tests check that everything works correct as an instance method.
* bpo-26680: Updates documentation for Real.is_integer and built-ins int and float.
The call x.is_integer() is now listed in the table of operations
which apply to all numeric types except complex, with a reference
to the full documentation for Real.is_integer(). Mention of
is_integer() has been removed from the section 'Additional Methods
on Float'.
The documentation for Real.is_integer() describes its purpose, and
mentions that it should be overridden for performance reasons, or
to handle special values like NaN.
* bpo-26680: Adds Decimal.is_integer to the Python and C implementations.
The C implementation of Decimal already implements and uses
mpd_isinteger internally, we just expose the existing function to
Python.
The Python implementation uses internal conversion to integer
using to_integral_value().
In both cases, the corresponding context methods are also
implemented.
Tests and documentation are included.
* bpo-26680: Updates the ACKS file.
* bpo-26680: NEWS entries for int, the numeric ABCs and Decimal.
Co-authored-by: Robert Smallshire <rob@sixty-north.com>
diff --git a/Lib/numbers.py b/Lib/numbers.py
index ed815ef..0634f62 100644
--- a/Lib/numbers.py
+++ b/Lib/numbers.py
@@ -148,7 +148,7 @@
"""To Complex, Real adds the operations that work on real numbers.
In short, those are: a conversion to float, trunc(), divmod,
- %, <, <=, >, and >=.
+ is_integer, %, <, <=, >, and >=.
Real also provides defaults for the derived operations.
"""
@@ -242,6 +242,17 @@
"""self <= other"""
raise NotImplementedError
+ def is_integer(self):
+ """Return True if the Real is integral; otherwise return False.
+
+ This default implementation can be overridden in subclasses
+ for performance reasons or to deal with values such as NaN,
+ which would otherwise cause an exception to be raised.
+ """
+ # Although __int__ is not defined at this level, the int
+ # constructor falls back to __trunc__, which we do have.
+ return self == int(self)
+
# Concrete implementations of Complex abstract methods.
def __complex__(self):
"""complex(self) == complex(float(self), 0)"""
@@ -290,6 +301,10 @@
"""
return self.numerator / self.denominator
+ def is_integer(self):
+ """Return True if the Rational is integral; otherwise return False."""
+ return self.denominator == 1
+
class Integral(Rational):
"""Integral adds a conversion to int and the bit-string operations."""
@@ -386,4 +401,8 @@
"""Integers have a denominator of 1."""
return 1
+ def is_integer(self):
+ """Return True; all Integrals represent an integral value."""
+ return True
+
Integral.register(int)