gh-86388 Remove deprecated behaviors in randrange() (#92677)

rhettinger · web-flow · commit 68fec31364e9 · 2022-05-11T23:54:51.000-05:00
diff --git a/Doc/library/random.rst b/Doc/library/random.rst
@@ -123,27 +123,26 @@ Functions for integers
 .. function:: randrange(stop)
               randrange(start, stop[, step])
 
-   Return a randomly selected element from ``range(start, stop, step)``.  This is
-   equivalent to ``choice(range(start, stop, step))``, but doesn't actually build a
-   range object.
+   Return a randomly selected element from ``range(start, stop, step)``.
 
-   The positional argument pattern matches that of :func:`range`.  Keyword arguments
-   should not be used because the function may use them in unexpected ways.
+   This is roughly equivalent to ``choice(range(start, stop, step))`` but
+   supports arbitrarily large ranges and is optimized for common cases.
+
+   The positional argument pattern matches the :func:`range` function.
+
+   Keyword arguments should not be used because they can interpreted
+   in unexpected ways. For example ``range(start=100)`` is interpreted
+   as ``range(0, 100, 1)``.
 
    .. versionchanged:: 3.2
       :meth:`randrange` is more sophisticated about producing equally distributed
       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:: 3.12
+      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)
 
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
@@ -102,8 +102,6 @@ Deprecated
 Removed
 =======
 
-
-
 Porting to Python 3.12
 ======================
 
@@ -120,6 +118,14 @@ Changes in the Python API
   contain ASCII letters and digits and underscore.
   (Contributed by Serhiy Storchaka in :gh:`91760`.)
 
+* Removed randrange() functionality deprecated since Python 3.10.  Formerly,
+  randrange(10.0) losslessly converted to randrange(10). Now, it raises a
+  TypeError. Also, the exception raised for non-integral values such as
+  randrange(10.5) or randrange('10') has been changed from ValueError to
+  TypeError.  This also prevents bugs where ``randrange(1e25)`` would silently
+  select from a larger range than ``randrange(10**25)``.
+  (Originally suggested by Serhiy Storchaka gh-86388.)
+
 
 Build Changes
 =============
diff --git a/Lib/random.py b/Lib/random.py
@@ -282,67 +282,34 @@ 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.
             if step is not _ONE:
-                raise TypeError('Missing a non-None stop argument')
+                raise TypeError("Missing a non-None stop argument")
             if istart > 0:
                 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})")
 
         # Non-unit step argument supplied.
         if istep > 0:
@@ -352,7 +319,7 @@ 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):
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
@@ -485,50 +485,44 @@ 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)
-
-    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)
+        raises_value_error(3, 3)
+        raises_value_error(-721)
+        raises_value_error(0, 100, -12)
+
+        # Zero step
+        raises_value_error(0, 42, 0)
+        raises_type_error(0, 42, 0.0)
+        raises_type_error(0, 0, 0.0)
+
+        # Non-integer stop
+        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')
+        raises_type_error(0, 2.71827, 2)
+
+        # Non-integer start
+        raises_type_error(2.71827, 5)
+        raises_type_error(2.0, 5)
+        raises_type_error(Fraction(2, 1), 5)
+        raises_type_error('2', 5)
+        raises_type_error(2.71827, 5, 2)
+
+        # Non-integer step
+        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_step(self):
         # bpo-42772: When stop is None, the step argument was being ignored.
diff --git a/Misc/NEWS.d/next/Library/2022-05-11-10-06-31.gh-issue-86388.7ivUtT.rst b/Misc/NEWS.d/next/Library/2022-05-11-10-06-31.gh-issue-86388.7ivUtT.rst
@@ -0,0 +1,5 @@
+Removed randrange() functionality deprecated since Python 3.10.  Formerly,
+randrange(10.0) losslessly converted to randrange(10). Now, it raises a
+TypeError. Also, the exception raised for non-integral values such as
+randrange(10.5) or randrange('10') has been changed from ValueError to
+TypeError.
