Break a loop between _pydecimal and _pylong.

serhiy-storchaka · serhiy-storchaka · commit 6f270bd23ca3 · 2024-05-02T16:25:28.000+03:00
diff --git a/Lib/_pylong.py b/Lib/_pylong.py
@@ -16,6 +16,9 @@
 import decimal
 
 
+_is_pydecimal = hasattr(decimal.Decimal, '_power_exact')
+
+
 def int_to_decimal(n):
     """Asymptotically fast conversion of an 'int' to Decimal."""
 
@@ -83,7 +86,7 @@ def inner(n, w):
 def int_to_decimal_string(n):
     """Asymptotically fast conversion of an 'int' to a decimal string."""
     w = n.bit_length()
-    if w > 900_000:
+    if w > 900_000 and not _is_pydecimal:
         return str(int_to_decimal(n))
 
     def inner(n, w):
@@ -103,6 +106,7 @@ def inner(n, w):
     else:
         return inner(n, w)
 
+
 def _str_to_int_inner(s):
     """Asymptotically fast conversion of a 'str' to an 'int'."""
 
diff --git a/Lib/test/test_int.py b/Lib/test/test_int.py
@@ -829,17 +829,40 @@ def tearDown(self):
         sys.set_int_max_str_digits(self._previous_limit)
         super().tearDown()
 
-    def test_pylong_int_to_decimal(self):
-        n = (1 << 100_000) - 1
-        suffix = '9883109375'
+    def _test_pylong_int_to_decimal(self, n, suffix):
         s = str(n)
-        assert s[-10:] == suffix
-        s = str(-n)
-        assert s[-10:] == suffix
-        s = '%d' % n
-        assert s[-10:] == suffix
-        s = b'%d' % n
-        assert s[-10:] == suffix.encode('ascii')
+        self.assertEqual(s[-10:], suffix)
+        s2 = str(-n)
+        self.assertEqual(s2, '-' + s)
+        s3 = '%d' % n
+        self.assertEqual(s3, s)
+        s4 = b'%d' % n
+        self.assertEqual(s4, s.encode('ascii'))
+
+    def test_pylong_int_to_decimal(self):
+        def check(n, suffix):
+            s = str(n)
+            self.assertEqual(s[-10:], suffix)
+            s2 = str(-n)
+            self.assertEqual(s2, '-' + s)
+            s3 = '%d' % n
+            self.assertEqual(s3, s)
+            s4 = b'%d' % n
+            self.assertEqual(s4, s.encode('ascii'))
+
+        self._test_pylong_int_to_decimal((1 << 100_000), '9883109376')
+        self._test_pylong_int_to_decimal((1 << 100_000) - 1, '9883109375')
+        self._test_pylong_int_to_decimal(10**30_000, '0000000000')
+        self._test_pylong_int_to_decimal(10**30_000 - 1, '9999999999')
+        self._test_pylong_int_to_decimal(3**60_000, '9313200001')
+
+    @support.requires_resource('cpu')
+    def test_pylong_int_to_decimal_2(self):
+        self._test_pylong_int_to_decimal(2**1_000_000, '2747109376')
+        self._test_pylong_int_to_decimal(2**1_000_000 - 1, '2747109375')
+        self._test_pylong_int_to_decimal(10**300_000, '0000000000')
+        self._test_pylong_int_to_decimal(10**300_000 - 1, '9999999999')
+        self._test_pylong_int_to_decimal(3**600_000, '3132000001')
 
     def test_pylong_int_divmod(self):
         n = (1 << 100_000)
diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-05-02-15-57-07.gh-issue-118164.AF6kwI.rst b/Misc/NEWS.d/next/Core and Builtins/2024-05-02-15-57-07.gh-issue-118164.AF6kwI.rst
@@ -0,0 +1,4 @@
+Break a loop between the Python implementation of the :mod:`decimal` module
+and the Python code for integer to string conversion. Optimize integer to
+string conversion for values in the range from 10_000 to 270_000 decimal
+digits.
