bpo-44258: support PEP 515 for Fraction's initialization from string

Lib/fractions.py

@@ -21,17 +21,17 @@
 _PyHASH_INF = sys.hash_info.inf
 
 _RATIONAL_FORMAT = re.compile(r"""
-    \A\s*                      # optional whitespace at the start, then
-    (?P<sign>[-+]?)            # an optional sign, then
-    (?=\d|\.\d)                # lookahead for digit or .digit
-    (?P<num>\d*)               # numerator (possibly empty)
-    (?:                        # followed by
-       (?:/(?P<denom>\d+))?    # an optional denominator
-    |                          # or
-       (?:\.(?P<decimal>\d*))? # an optional fractional part
-       (?:E(?P<exp>[-+]?\d+))? # and optional exponent
+    \A\s*                                    # optional whitespace at the start,
+    (?P<sign>[-+]?)                          # an optional sign, then
+    (?=\d|\.\d)                              # lookahead for digit or .digit
+    (?P<num>((\d+_?)*\d|\d*))                # numerator (possibly empty)
+    (?:                                      # followed by
+       (?:/(?P<den>(\d+_?)*\d+))?            # an optional denominator
+    |                                        # or
+       (?:\.(?P<decimal>((\d+_?)*\d|\d*)))?  # an optional fractional part
+       (?:E(?P<exp>[-+]?(\d+_?)*\d+))?       # and optional exponent
     )
-    \s*\Z                      # and optional whitespace to finish
+    \s*\Z                                    # and optional whitespace to finish
 """, re.VERBOSE | re.IGNORECASE)
 
 
@@ -115,15 +115,16 @@ def __new__(cls, numerator=0, denominator=None, *, _normalize=True):
                     raise ValueError('Invalid literal for Fraction: %r' %
                                      numerator)
                 numerator = int(m.group('num') or '0')
-                denom = m.group('denom')
-                if denom:
-                    denominator = int(denom)
+                denominator = m.group('den')
+                if denominator:
+                    denominator = int(denominator)
                 else:
                     denominator = 1
                     decimal = m.group('decimal')
                     if decimal:
-                        scale = 10**len(decimal)
-                        numerator = numerator * scale + int(decimal)
+                        decimal = int(decimal)
+                        scale = 10**len(str(decimal))
+                        numerator = numerator * scale + decimal
                         denominator *= scale
                     exp = m.group('exp')
                     if exp:

Lib/test/test_fractions.py

@@ -173,6 +173,10 @@ def testFromString(self):
         self.assertEqual((-12300, 1), _components(F("-1.23e4")))
         self.assertEqual((0, 1), _components(F(" .0e+0\t")))
         self.assertEqual((0, 1), _components(F("-0.000e0")))
+        self.assertEqual((123, 1), _components(F("1_2_3")))
+        self.assertEqual((41, 107), _components(F("1_2_3/3_2_1")))
+        self.assertEqual((6283, 2000), _components(F("3.14_15")))
+        self.assertEqual((6283, 2*10**13), _components(F("3.14_15e-1_0")))
 
         self.assertRaisesMessage(
             ZeroDivisionError, "Fraction(3, 0)",
@@ -210,6 +214,60 @@ def testFromString(self):
             # Allow 3. and .3, but not .
             ValueError, "Invalid literal for Fraction: '.'",
             F, ".")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '_'",
+            F, "_")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1_'",
+            F, "1_")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '_1'",
+            F, "_1")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1__2'",
+            F, "1__2")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '/_'",
+            F, "/_")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1_/'",
+            F, "1_/")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '_1/'",
+            F, "_1/")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1__2/'",
+            F, "1__2/")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1/_'",
+            F, "1/_")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1/1_'",
+            F, "1/1_")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1/_1'",
+            F, "1/_1")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1/1__2'",
+            F, "1/1__2")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1._111'",
+            F, "1._111")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1.1__1'",
+            F, "1.1__1")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1.1_'",
+            F, "1.1_")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1.1e+_1'",
+            F, "1.1e+_1")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1.1e+1_'",
+            F, "1.1e+1_")
+        self.assertRaisesMessage(
+            ValueError, "Invalid literal for Fraction: '1.1e+1__1'",
+            F, "1.1e+1__1")
 
     def testImmutable(self):
         r = F(7, 3)

Misc/NEWS.d/next/Library/2021-05-28-09-43-33.bpo-44258.nh5F7R.rst

@@ -0,0 +1 @@
+Support PEP 515 for Fraction's initialization from string.