bpo-42222: Modernize integer test/conversion in randrange() (#23064)

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Raymond Hettinger 2020-12-28 11:10:34 -08:00 committed by GitHub
parent 1031f23fc3
commit a9621bb301
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4 changed files with 81 additions and 11 deletions

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@ -135,6 +135,15 @@ Functions for integers
values. Formerly it used a style like ``int(random()*n)`` which could produce values. Formerly it used a style like ``int(random()*n)`` which could produce
slightly uneven distributions. slightly uneven distributions.
.. deprecated:: 3.10
The automatic conversion of non-integer types to equivalent integers is
deprecated. Currently ``randrange(10.0)`` is losslessly converted to
``randrange(10)``. In the future, this will raise a :exc:`TypeError`.
.. deprecated:: 3.10
The exception raised for non-integral values such as ``range(10.5)``
will be changed from :exc:`ValueError` to :exc:`TypeError`.
.. function:: randint(a, b) .. function:: randint(a, b)
Return a random integer *N* such that ``a <= N <= b``. Alias for Return a random integer *N* such that ``a <= N <= b``. Alias for

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@ -51,6 +51,7 @@ from math import sqrt as _sqrt, acos as _acos, cos as _cos, sin as _sin
from math import tau as TWOPI, floor as _floor, isfinite as _isfinite from math import tau as TWOPI, floor as _floor, isfinite as _isfinite
from os import urandom as _urandom from os import urandom as _urandom
from _collections_abc import Set as _Set, Sequence as _Sequence from _collections_abc import Set as _Set, Sequence as _Sequence
from operator import index as _index
from itertools import accumulate as _accumulate, repeat as _repeat from itertools import accumulate as _accumulate, repeat as _repeat
from bisect import bisect as _bisect from bisect import bisect as _bisect
import os as _os import os as _os
@ -297,28 +298,59 @@ class Random(_random.Random):
# This code is a bit messy to make it fast for the # This code is a bit messy to make it fast for the
# common case while still doing adequate error checking. # common case while still doing adequate error checking.
istart = int(start) try:
if istart != start: istart = _index(start)
raise ValueError("non-integer arg 1 for randrange()") except TypeError:
if int(start) == start:
istart = int(start)
_warn('Float arguments to randrange() have been deprecated\n'
'since Python 3.10 and will be removed in a subsequent '
'version.',
DeprecationWarning, 2)
else:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer arg 1 for randrange()")
if stop is None: if stop is None:
if istart > 0: if istart > 0:
return self._randbelow(istart) return self._randbelow(istart)
raise ValueError("empty range for randrange()") raise ValueError("empty range for randrange()")
# stop argument supplied. # stop argument supplied.
istop = int(stop) try:
if istop != stop: istop = _index(stop)
raise ValueError("non-integer stop for randrange()") except TypeError:
if int(stop) == stop:
istop = int(stop)
_warn('Float arguments to randrange() have been deprecated\n'
'since Python 3.10 and will be removed in a subsequent '
'version.',
DeprecationWarning, 2)
else:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer stop for randrange()")
try:
istep = _index(step)
except TypeError:
if int(step) == step:
istep = int(step)
_warn('Float arguments to randrange() have been deprecated\n'
'since Python 3.10 and will be removed in a subsequent '
'version.',
DeprecationWarning, 2)
else:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer step for randrange()")
width = istop - istart width = istop - istart
if step == 1 and width > 0: if istep == 1 and width > 0:
return istart + self._randbelow(width) return istart + self._randbelow(width)
if step == 1: if istep == 1:
raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width)) raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))
# Non-unit step argument supplied. # Non-unit step argument supplied.
istep = int(step)
if istep != step:
raise ValueError("non-integer step for randrange()")
if istep > 0: if istep > 0:
n = (width + istep - 1) // istep n = (width + istep - 1) // istep
elif istep < 0: elif istep < 0:

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@ -542,6 +542,26 @@ class SystemRandom_TestBasicOps(TestBasicOps, unittest.TestCase):
raises(0, 42, 0) raises(0, 42, 0)
raises(0, 42, 3.14159) raises(0, 42, 3.14159)
def test_randrange_argument_handling(self):
randrange = self.gen.randrange
with self.assertWarns(DeprecationWarning):
randrange(10.0, 20, 2)
with self.assertWarns(DeprecationWarning):
randrange(10, 20.0, 2)
with self.assertWarns(DeprecationWarning):
randrange(10, 20, 1.0)
with self.assertWarns(DeprecationWarning):
randrange(10, 20, 2.0)
with self.assertWarns(DeprecationWarning):
with self.assertRaises(ValueError):
randrange(10.5)
with self.assertWarns(DeprecationWarning):
with self.assertRaises(ValueError):
randrange(10, 20.5)
with self.assertWarns(DeprecationWarning):
with self.assertRaises(ValueError):
randrange(10, 20, 1.5)
def test_randbelow_logic(self, _log=log, int=int): def test_randbelow_logic(self, _log=log, int=int):
# check bitcount transition points: 2**i and 2**(i+1)-1 # check bitcount transition points: 2**i and 2**(i+1)-1
# show that: k = int(1.001 + _log(n, 2)) # show that: k = int(1.001 + _log(n, 2))

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@ -0,0 +1,9 @@
Harmonized random.randrange() argument handling to match range().
* The integer test and conversion in randrange() now uses
operator.index().
* Non-integer arguments to randrange() are deprecated.
* The *ValueError* is deprecated in favor of a *TypeError*.
* It now runs a little faster than before.
(Contributed by Raymond Hettinger and Serhiy Storchaka.)