Updated fractions + test_fractions

RustPython · terryluan12 · Dec 30, 2025 · Dec 30, 2025 · Dec 30, 2025 · Dec 30, 2025
commit aae2dcfde4bc162c9f9d0007c0e7a918deb9163c
diff --git a/Lib/fractions.py b/Lib/fractions.py
@@ -139,6 +139,23 @@ def _round_to_figures(n, d, figures):
     return sign, significand, exponent
 
 
+# Pattern for matching non-float-style format specifications.
+_GENERAL_FORMAT_SPECIFICATION_MATCHER = re.compile(r"""
+    (?:
+        (?P<fill>.)?
+        (?P<align>[<>=^])
+    )?
+    (?P<sign>[-+ ]?)
+    # Alt flag forces a slash and denominator in the output, even for
+    # integer-valued Fraction objects.
+    (?P<alt>\#)?
+    # We don't implement the zeropad flag since there's no single obvious way
+    # to interpret it.
+    (?P<minimumwidth>0|[1-9][0-9]*)?
+    (?P<thousands_sep>[,_])?
+""", re.DOTALL | re.VERBOSE).fullmatch
+
+
 # Pattern for matching float-style format specifications;
 # supports 'e', 'E', 'f', 'F', 'g', 'G' and '%' presentation types.
 _FLOAT_FORMAT_SPECIFICATION_MATCHER = re.compile(r"""
@@ -414,27 +431,42 @@ def __str__(self):
         else:
             return '%s/%s' % (self._numerator, self._denominator)
 
-    def __format__(self, format_spec, /):
-        """Format this fraction according to the given format specification."""
-
-        # Backwards compatiblility with existing formatting.
-        if not format_spec:
-            return str(self)
+    def _format_general(self, match):
+        """Helper method for __format__.
 
+        Handles fill, alignment, signs, and thousands separators in the
+        case of no presentation type.
+        """
         # Validate and parse the format specifier.
-        match = _FLOAT_FORMAT_SPECIFICATION_MATCHER(format_spec)
-        if match is None:
-            raise ValueError(
-                f"Invalid format specifier {format_spec!r} "
-                f"for object of type {type(self).__name__!r}"
-            )
-        elif match["align"] is not None and match["zeropad"] is not None:
-            # Avoid the temptation to guess.
-            raise ValueError(
-                f"Invalid format specifier {format_spec!r} "
-                f"for object of type {type(self).__name__!r}; "
-                "can't use explicit alignment when zero-padding"
-            )
+        fill = match["fill"] or " "
+        align = match["align"] or ">"
+        pos_sign = "" if match["sign"] == "-" else match["sign"]
+        alternate_form = bool(match["alt"])
+        minimumwidth = int(match["minimumwidth"] or "0")
+        thousands_sep = match["thousands_sep"] or ''
+
+        # Determine the body and sign representation.
+        n, d = self._numerator, self._denominator
+        if d > 1 or alternate_form:
+            body = f"{abs(n):{thousands_sep}}/{d:{thousands_sep}}"
+        else:
+            body = f"{abs(n):{thousands_sep}}"
+        sign = '-' if n < 0 else pos_sign
+
+        # Pad with fill character if necessary and return.
+        padding = fill * (minimumwidth - len(sign) - len(body))
+        if align == ">":
+            return padding + sign + body
+        elif align == "<":
+            return sign + body + padding
+        elif align == "^":
+            half = len(padding) // 2
+            return padding[:half] + sign + body + padding[half:]
+        else:  # align == "="
+            return sign + padding + body
+
+    def _format_float_style(self, match):
+        """Helper method for __format__; handles float presentation types."""
         fill = match["fill"] or " "
         align = match["align"] or ">"
         pos_sign = "" if match["sign"] == "-" else match["sign"]
@@ -449,6 +481,9 @@ def __format__(self, format_spec, /):
         trim_point = not alternate_form
         exponent_indicator = "E" if presentation_type in "EFG" else "e"
 
+        if align == '=' and fill == '0':
+            zeropad = True
+
         # Round to get the digits we need, figure out where to place the point,
         # and decide whether to use scientific notation. 'point_pos' is the
         # relative to the _end_ of the digit string: that is, it's the number
@@ -530,7 +565,25 @@ def __format__(self, format_spec, /):
         else:  # align == "="
             return sign + padding + body
 
-    def _operator_fallbacks(monomorphic_operator, fallback_operator):
+    def __format__(self, format_spec, /):
+        """Format this fraction according to the given format specification."""
+
+        if match := _GENERAL_FORMAT_SPECIFICATION_MATCHER(format_spec):
+            return self._format_general(match)
+
+        if match := _FLOAT_FORMAT_SPECIFICATION_MATCHER(format_spec):
+            # Refuse the temptation to guess if both alignment _and_
+            # zero padding are specified.
+            if match["align"] is None or match["zeropad"] is None:
+                return self._format_float_style(match)
+
+        raise ValueError(
+            f"Invalid format specifier {format_spec!r} "
+            f"for object of type {type(self).__name__!r}"
+        )
+
+    def _operator_fallbacks(monomorphic_operator, fallback_operator,
+                            handle_complex=True):
         """Generates forward and reverse operators given a purely-rational
         operator and a function from the operator module.
 
@@ -617,7 +670,7 @@ def forward(a, b):
                 return monomorphic_operator(a, Fraction(b))
             elif isinstance(b, float):
                 return fallback_operator(float(a), b)
-            elif isinstance(b, complex):
+            elif handle_complex and isinstance(b, complex):
                 return fallback_operator(complex(a), b)
             else:
                 return NotImplemented
@@ -630,7 +683,7 @@ def reverse(b, a):
                 return monomorphic_operator(Fraction(a), b)
             elif isinstance(a, numbers.Real):
                 return fallback_operator(float(a), float(b))
-            elif isinstance(a, numbers.Complex):
+            elif handle_complex and isinstance(a, numbers.Complex):
                 return fallback_operator(complex(a), complex(b))
             else:
                 return NotImplemented
@@ -781,22 +834,22 @@ def _floordiv(a, b):
         """a // b"""
         return (a.numerator * b.denominator) // (a.denominator * b.numerator)
 
-    __floordiv__, __rfloordiv__ = _operator_fallbacks(_floordiv, operator.floordiv)
+    __floordiv__, __rfloordiv__ = _operator_fallbacks(_floordiv, operator.floordiv, False)
 
     def _divmod(a, b):
         """(a // b, a % b)"""
         da, db = a.denominator, b.denominator
         div, n_mod = divmod(a.numerator * db, da * b.numerator)
         return div, Fraction(n_mod, da * db)
 
-    __divmod__, __rdivmod__ = _operator_fallbacks(_divmod, divmod)
+    __divmod__, __rdivmod__ = _operator_fallbacks(_divmod, divmod, False)
 
     def _mod(a, b):
         """a % b"""
         da, db = a.denominator, b.denominator
         return Fraction((a.numerator * db) % (b.numerator * da), da * db)
 
-    __mod__, __rmod__ = _operator_fallbacks(_mod, operator.mod)
+    __mod__, __rmod__ = _operator_fallbacks(_mod, operator.mod, False)
 
     def __pow__(a, b):
         """a ** b
@@ -825,8 +878,10 @@ def __pow__(a, b):
                 # A fractional power will generally produce an
                 # irrational number.
                 return float(a) ** float(b)
-        else:
+        elif isinstance(b, (float, complex)):
             return float(a) ** b
+        else:
+            return NotImplemented
 
     def __rpow__(b, a):
         """a ** b"""