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bpo-37319: Deprecated support of non-integer arguments in random.randrange(). #19112

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Merged
serhiy-storchaka merged 10 commits into from
Jan 25, 2021
Merged

bpo-37319: Deprecated support of non-integer arguments in random.randrange(). #19112

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9f81ab8
Use index() instead of int() to check args of randrange().
serhiy-storchaka Jun 22, 2019
ccff52e
Fallaback to int().
serhiy-storchaka Mar 22, 2020
fb9382e
Merge branch 'master' into randrange-index
serhiy-storchaka Oct 31, 2020
fcd6549
Remove _ONE.
serhiy-storchaka Oct 31, 2020
2e8cfda
Raise TypeError instead of ValueError.
serhiy-storchaka Oct 31, 2020
d2925e6
Merge branch 'master' into randrange-index
serhiy-storchaka Dec 24, 2020
6ff20ab
Revert "Raise TypeError instead of ValueError."
serhiy-storchaka Dec 24, 2020
3ad3c36
Update docs and emit deprecation warning for ValueError.
serhiy-storchaka Dec 24, 2020
5749575
Merge branch 'master' into randrange-index
serhiy-storchaka Dec 28, 2020
d5dec67
Merge branch 'master' into randrange-index
serhiy-storchaka Jan 24, 2021
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Fallaback to int().
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@serhiy-storchaka
serhiy-storchaka committed Mar 22, 2020
commit ccff52ec138142d4825ea9d1a9a377f1440b01f7
4 changes: 4 additions & 0 deletions Doc/library/random.rst
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Expand Up @@ -130,6 +130,10 @@ Functions for integers
values. Formerly it used a style like ``int(random()*n)`` which could produce
slightly uneven distributions.

.. deprecated:: 3.9
Accepting non-integer arguments is deprecated.


.. function:: randint(a, b)

Return a random integer *N* such that ``a <= N <= b``. Alias for
Expand Down
3 changes: 3 additions & 0 deletions Doc/whatsnew/3.9.rst
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Expand Up @@ -612,6 +612,9 @@ Deprecated
by :c:func:`Py_Initialize()` since Python 3.7.
(Contributed by Victor Stinner in :issue:`39877`.)

* Deprecated support of non-integer arguments in :func:`random.randrange`.
(Contributed by Serhiy Storchaka in :issue:`37319`.)


Removed
=======
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56 changes: 39 additions & 17 deletions Lib/random.py
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Expand Up @@ -68,7 +68,7 @@
SG_MAGICCONST = 1.0 + _log(4.5)
BPF = 53 # Number of bits in a float
RECIP_BPF = 2**-BPF

_ONE = 1
Comment thread
serhiy-storchaka marked this conversation as resolved.

# Translated by Guido van Rossum from C source provided by
# Adrian Baddeley. Adapted by Raymond Hettinger for use with
Expand Down Expand Up @@ -209,7 +209,7 @@ def __reduce__(self):

## -------------------- integer methods -------------------

def randrange(self, start, stop=None, step=1, _index=_index):
def randrange(self, start, stop=None, step=_ONE, _index=_index, _int=int):
"""Choose a random item from range(start, stop[, step]).

This fixes the problem with randint() which includes the
Expand All @@ -219,33 +219,55 @@ def randrange(self, start, stop=None, step=1, _index=_index):

# This code is a bit messy to make it fast for the
# common case while still doing adequate error checking.
start = _index(start)
try:
istart = _index(start)
except TypeError:
istart = _int(start)
if istart != start:
raise ValueError("non-integer arg 1 for randrange()")
_warn('non-integer arg 1 for randrange()',
DeprecationWarning, 2)
if stop is None:
if start > 0:
return self._randbelow(start)
if istart > 0:
return self._randbelow(istart)
raise ValueError("empty range for randrange()")

# stop argument supplied.
stop = _index(stop)
width = stop - start
if step == 1 and width > 0:
return start + self._randbelow(width)
if step == 1:
raise ValueError("empty range for randrange() (%d, %d, %d)" % (start, stop, width))
try:
istop = _index(stop)
except TypeError:
istop = _int(stop)
if istop != stop:
raise ValueError("non-integer stop for randrange()")
_warn('non-integer stop for randrange()',
DeprecationWarning, 2)
width = istop - istart
# Fast path.
if step is _ONE:
if width > 0:
return istart + self._randbelow(width)
raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width))

# Non-unit step argument supplied.
step = _index(step)
if step > 0:
n = (width + step - 1) // step
elif step < 0:
n = (width + step + 1) // step
try:
istep = _index(step)
except TypeError:
istep = _int(step)
if istep != step:
raise ValueError("non-integer step for randrange()")

@rhettinger rhettinger Oct 31, 2020

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While we're at it, the exception type should be converted to TypeError.

@serhiy-storchaka serhiy-storchaka Oct 31, 2020

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Should we raise it with custom message or reraise the exception raised by index()?

_warn('non-integer step for randrange()',
DeprecationWarning, 2)
if istep > 0:
n = (width + istep - 1) // istep
elif istep < 0:
n = (width + istep + 1) // istep
else:
raise ValueError("zero step for randrange()")

if n <= 0:
raise ValueError("empty range for randrange()")

return start + step*self._randbelow(n)
return istart + istep*self._randbelow(n)

def randint(self, a, b):
"""Return random integer in range [a, b], including both end points.
Expand Down
19 changes: 13 additions & 6 deletions Lib/test/test_random.py
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Expand Up @@ -367,15 +367,22 @@ def test_randrange_errors(self):
raises(3, 3)
raises(-721)
raises(0, 100, -12)
self.assertWarns(DeprecationWarning, raises, 3, 3, 1.0)
# Non-integer start/stop
self.assertRaises(TypeError, self.gen.randrange, 3.0)
self.assertRaises(TypeError, self.gen.randrange, Fraction(3, 1))
self.assertRaises(TypeError, self.gen.randrange, 0, 2.0)
self.assertRaises(TypeError, self.gen.randrange, 0, Fraction(2, 1))
raises(3.14159)
self.assertWarns(DeprecationWarning, self.gen.randrange, 3.0)
self.assertWarns(DeprecationWarning, self.gen.randrange, Fraction(3, 1))
raises('3')
raises(0, 2.71828)
self.assertWarns(DeprecationWarning, self.gen.randrange, 0, 2.0)
self.assertWarns(DeprecationWarning, self.gen.randrange, 0, Fraction(2, 1))
raises(0, '2')
# Zero and non-integer step
raises(0, 42, 0)
self.assertRaises(TypeError, self.gen.randrange, 0, 42, 3.0)
self.assertRaises(TypeError, self.gen.randrange, 0, 42, Fraction(3, 1))
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))
raises(0, 42, '3')

def test_genrandbits(self):
# Verify ranges
Expand Down
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2020-03-22-21-33-31.bpo-37319.BrIAir.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Deprecated support of non-integer arguments in :func:`random.randrange`.