bpo-37319: Improve documentation, code and tests of randrange. (GH-19112)

2 files changed, 36 insertions, 27 deletions

diff --git a/Lib/random.py b/Lib/random.py
index 30186fc7a3..187b0a0169 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -303,17 +303,15 @@ class Random(_random.Random):
         try:
             istart = _index(start)
         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:
+            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)
         if stop is None:
             # We don't check for "step != 1" because it hasn't been
             # type checked and converted to an integer yet.
@@ -327,31 +325,29 @@ class Random(_random.Random):
         try:
             istop = _index(stop)
         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:
+            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)
+        width = istop - istart
         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:
+            istep = int(step)
+            if istep != step:
                 _warn('randrange() will raise TypeError in the future',
                       DeprecationWarning, 2)
                 raise ValueError("non-integer step for randrange()")
-        width = istop - istart
+            _warn('non-integer arguments to randrange() have been deprecated '
+                  'since Python 3.10 and will be removed in a subsequent '
+                  'version',
+                  DeprecationWarning, 2)
+        # Fast path.
         if istep == 1:
             if width > 0:
                 return istart + self._randbelow(width)
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index 35ae4e6c3c..66908868a6 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -509,11 +509,24 @@ class SystemRandom_TestBasicOps(TestBasicOps, unittest.TestCase):
         raises(-721)
         raises(0, 100, -12)
         # Non-integer start/stop
-        raises(3.14159)
-        raises(0, 2.71828)
+        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)
-        raises(0, 42, 3.14159)
+        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