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bpo-42222: Remove deprecated support for non-integer values #28983

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Oct 16, 2021
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bpo-42222: Remove deprecated support for non-integer values #28983

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8cf5d54
Remove deprecated non-integer support
rhettinger Oct 15, 2021
738e090
Add doc updates
rhettinger Oct 15, 2021
cc89346
Add blurb
rhettinger Oct 15, 2021
eb76fbd
index() version
rhettinger Oct 15, 2021
e509f7f
Update tests
rhettinger Oct 15, 2021
a87fcac
Tweek wording for the versionchanged entry
rhettinger Oct 15, 2021
59a734b
Improve test organization
rhettinger Oct 15, 2021
8fe5c51
Improve docstring
rhettinger Oct 15, 2021
9a014ea
More detailed error messages
rhettinger Oct 16, 2021
e7a217f
Improve docstring
rhettinger Oct 16, 2021
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13 changes: 4 additions & 9 deletions Doc/library/random.rst
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Expand Up @@ -135,15 +135,10 @@ Functions for integers
values. Formerly it used a style like ``int(random()*n)`` which could produce
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 ``randrange(10.5)``
or ``randrange('10')`` will be changed from :exc:`ValueError` to
:exc:`TypeError`.
.. versionchanged:: 3.11
Automatic conversion of non-integer types is no longer supported.
Calls such as ``randrange(10.0)`` and ``randrange(Fraction(10, 1))``
now raise a :exc:`TypeError`.

.. function:: randint(a, b)

Expand Down
52 changes: 10 additions & 42 deletions Lib/random.py
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Expand Up @@ -286,27 +286,17 @@ def randbytes(self, n):
## -------------------- integer methods -------------------

def randrange(self, start, stop=None, step=_ONE):
"""Choose a random item from range(start, stop[, step]).
"""Choose a random item from range(stop) or range(start, stop[, step]).

This fixes the problem with randint() which includes the
endpoint; in Python this is usually not what you want.
Roughly equivalent to ``choice(range(start, stop, step))``
but supports arbitrarily large ranges and is optimized
for common cases.

"""

# This code is a bit messy to make it fast for the
# common case while still doing adequate error checking.
try:
istart = _index(start)
except TypeError:
istart = int(start)
if istart != start:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer arg 1 for randrange()")
_warn('non-integer arguments to randrange() have been deprecated '
'since Python 3.10 and will be removed in a subsequent '
'version',
DeprecationWarning, 2)
istart = _index(start)
if stop is None:
# We don't check for "step != 1" because it hasn't been
# type checked and converted to an integer yet.
Expand All @@ -316,37 +306,15 @@ def randrange(self, start, stop=None, step=_ONE):
return self._randbelow(istart)
raise ValueError("empty range for randrange()")

# stop argument supplied.
try:
istop = _index(stop)
except TypeError:
istop = int(stop)
if istop != stop:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer stop for randrange()")
_warn('non-integer arguments to randrange() have been deprecated '
'since Python 3.10 and will be removed in a subsequent '
'version',
DeprecationWarning, 2)
# Stop argument supplied.
istop = _index(stop)
width = istop - istart
try:
istep = _index(step)
except TypeError:
istep = int(step)
if istep != step:
_warn('randrange() will raise TypeError in the future',
DeprecationWarning, 2)
raise ValueError("non-integer step for randrange()")
_warn('non-integer arguments to randrange() have been deprecated '
'since Python 3.10 and will be removed in a subsequent '
'version',
DeprecationWarning, 2)
istep = _index(step)
# Fast path.
if istep == 1:
if width > 0:
return istart + self._randbelow(width)
raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))
raise ValueError(f"empty range in randrange({start}, {stop}, {step})")

# Non-unit step argument supplied.
if istep > 0:
Expand All @@ -356,7 +324,7 @@ def randrange(self, start, stop=None, step=_ONE):
else:
raise ValueError("zero step for randrange()")
if n <= 0:
raise ValueError("empty range for randrange()")
raise ValueError(f"empty range in randrange({start}, {stop}, {step})")
return istart + istep * self._randbelow(n)

def randint(self, a, b):
Expand Down
75 changes: 39 additions & 36 deletions Lib/test/test_random.py
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Expand Up @@ -481,50 +481,53 @@ def test_randrange_nonunit_step(self):
self.assertEqual(rint, 0)

def test_randrange_errors(self):
raises = partial(self.assertRaises, ValueError, self.gen.randrange)
raises_value_error = partial(self.assertRaises, ValueError, self.gen.randrange)
raises_type_error = partial(self.assertRaises, TypeError, self.gen.randrange)

# Empty range
raises(3, 3)
raises(-721)
raises(0, 100, -12)
# Non-integer start/stop
self.assertWarns(DeprecationWarning, raises, 3.14159)
self.assertWarns(DeprecationWarning, self.gen.randrange, 3.0)
self.assertWarns(DeprecationWarning, self.gen.randrange, Fraction(3, 1))
self.assertWarns(DeprecationWarning, raises, '3')
self.assertWarns(DeprecationWarning, raises, 0, 2.71828)
self.assertWarns(DeprecationWarning, self.gen.randrange, 0, 2.0)
self.assertWarns(DeprecationWarning, self.gen.randrange, 0, Fraction(2, 1))
self.assertWarns(DeprecationWarning, raises, 0, '2')
# Zero and non-integer step
raises(0, 42, 0)
self.assertWarns(DeprecationWarning, raises, 0, 42, 0.0)
self.assertWarns(DeprecationWarning, raises, 0, 0, 0.0)
self.assertWarns(DeprecationWarning, raises, 0, 42, 3.14159)
self.assertWarns(DeprecationWarning, self.gen.randrange, 0, 42, 3.0)
self.assertWarns(DeprecationWarning, self.gen.randrange, 0, 42, Fraction(3, 1))
self.assertWarns(DeprecationWarning, raises, 0, 42, '3')
self.assertWarns(DeprecationWarning, self.gen.randrange, 0, 42, 1.0)
self.assertWarns(DeprecationWarning, raises, 0, 0, 1.0)
raises_value_error(3, 3)
raises_value_error(-721)
raises_value_error(0, 100, -12)

# Zero step
raises_value_error(0, 42, 0)

# Non-integer start/stop/step
raises_type_error(3.14159)
raises_type_error(3.0)
raises_type_error(Fraction(3, 1))
raises_type_error('3')
raises_type_error(0, 2.71827)
raises_type_error(0, 2.0)
raises_type_error(0, Fraction(2, 1))
raises_type_error(0, '2')

# Non-integer step
raises_type_error(0, 42, 1.0)
raises_type_error(0, 0, 1.0)
raises_type_error(0, 42, 3.14159)
raises_type_error(0, 42, 3.0)
raises_type_error(0, 42, Fraction(3, 1))
raises_type_error(0, 42, '3')
raises_type_error(0, 42, 1.0)
raises_type_error(0, 0, 1.0)

def test_randrange_argument_handling(self):
randrange = self.gen.randrange
with self.assertWarns(DeprecationWarning):
with self.assertRaises(TypeError):
randrange(10.0, 20, 2)
with self.assertWarns(DeprecationWarning):
with self.assertRaises(TypeError):
randrange(10, 20.0, 2)
with self.assertWarns(DeprecationWarning):
with self.assertRaises(TypeError):
randrange(10, 20, 1.0)
with self.assertWarns(DeprecationWarning):
with self.assertRaises(TypeError):
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)
with self.assertRaises(TypeError):
randrange(10.5)
with self.assertRaises(TypeError):
randrange(10, 20.5)
with self.assertRaises(TypeError):
randrange(10, 20, 1.5)

def test_randrange_step(self):
# bpo-42772: When stop is None, the step argument was being ignored.
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2021-10-15-11-30-11.bpo-42222.hdHyac.rst
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@@ -0,0 +1 @@
Removed deprecated support for float arguments in *randrange()*.