Merged revisions 60053-60078 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r60054 | christian.heimes | 2008-01-18 20:12:56 +0100 (Fri, 18 Jan 2008) | 1 line

  Silence Coverity false alerts with CIDs #172, #183, #184
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  r60057 | guido.van.rossum | 2008-01-18 21:56:30 +0100 (Fri, 18 Jan 2008) | 3 lines

  Fix an edge case whereby the __del__() method of a classic class could
  create a new weakref to the object.
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  r60058 | raymond.hettinger | 2008-01-18 22:14:58 +0100 (Fri, 18 Jan 2008) | 1 line

  Better variable name in an example.
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  r60063 | guido.van.rossum | 2008-01-19 00:05:40 +0100 (Sat, 19 Jan 2008) | 3 lines

  This got fixed for classic classes in r60057,
  and backported to 2.5.2 in 60056.
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  r60068 | jeffrey.yasskin | 2008-01-19 10:56:06 +0100 (Sat, 19 Jan 2008) | 4 lines

  Several tweaks: add construction from strings and .from_decimal(), change
  __init__ to __new__ to enforce immutability, and remove "rational." from repr
  and the parens from str.
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  r60069 | georg.brandl | 2008-01-19 11:11:27 +0100 (Sat, 19 Jan 2008) | 2 lines

  Fix markup.
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  r60070 | georg.brandl | 2008-01-19 11:16:09 +0100 (Sat, 19 Jan 2008) | 3 lines

  Amend curses docs by info how to write non-ascii characters.
  Thanks to Jeroen Ruigrok van der Werven.
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  r60071 | georg.brandl | 2008-01-19 11:18:07 +0100 (Sat, 19 Jan 2008) | 2 lines

  Indentation normalization.
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  r60073 | facundo.batista | 2008-01-19 13:32:27 +0100 (Sat, 19 Jan 2008) | 5 lines


  Fix issue #1822: MIMEMultipart.is_multipart() behaves correctly for a
  just-created (and empty) instance.  Added tests for this. Thanks
  Jonathan Share.
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  r60074 | andrew.kuchling | 2008-01-19 14:33:20 +0100 (Sat, 19 Jan 2008) | 1 line

  Polish sentence
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  r60075 | christian.heimes | 2008-01-19 14:46:06 +0100 (Sat, 19 Jan 2008) | 1 line

  Added unit test to verify that threading.local doesn't cause ref leaks. It seems that the thread local storage always keeps the storage of the last stopped thread alive. Can anybody comment on it, please?
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  r60076 | christian.heimes | 2008-01-19 16:06:09 +0100 (Sat, 19 Jan 2008) | 1 line

  Update for threading.local test.
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  r60077 | andrew.kuchling | 2008-01-19 16:16:37 +0100 (Sat, 19 Jan 2008) | 1 line

  Polish sentence
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  r60078 | georg.brandl | 2008-01-19 16:22:16 +0100 (Sat, 19 Jan 2008) | 2 lines

  Fix typos.
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1 files changed, 64 insertions, 12 deletions

diff --git a/Lib/rational.py b/Lib/rational.py
index c913ec7..71ffff7 100755
--- a/Lib/rational.py
+++ b/Lib/rational.py
@@ -6,6 +6,7 @@
 import math
 import numbers
 import operator
+import re
 
 __all__ = ["Rational"]
 
@@ -75,6 +76,10 @@ def _binary_float_to_ratio(x):
         return (top, 2 ** -e)
 
 
+_RATIONAL_FORMAT = re.compile(
+    r'^\s*(?P<sign>[-+]?)(?P<num>\d+)(?:/(?P<denom>\d+))?\s*$')
+
+
 class Rational(RationalAbc):
     """This class implements rational numbers.
 
@@ -83,18 +88,41 @@ class Rational(RationalAbc):
     and the denominator defaults to 1 so that Rational(3) == 3 and
     Rational() == 0.
 
+    Rationals can also be constructed from strings of the form
+    '[-+]?[0-9]+(/[0-9]+)?', optionally surrounded by spaces.
+
     """
 
     __slots__ = ('_numerator', '_denominator')
 
-    def __init__(self, numerator=0, denominator=1):
-        if (not isinstance(numerator, numbers.Integral) and
-            isinstance(numerator, RationalAbc) and
-            denominator == 1):
-            # Handle copies from other rationals.
-            other_rational = numerator
-            numerator = other_rational.numerator
-            denominator = other_rational.denominator
+    # We're immutable, so use __new__ not __init__
+    def __new__(cls, numerator=0, denominator=1):
+        """Constructs a Rational.
+
+        Takes a string, another Rational, or a numerator/denominator pair.
+
+        """
+        self = super(Rational, cls).__new__(cls)
+
+        if denominator == 1:
+            if isinstance(numerator, str):
+                # Handle construction from strings.
+                input = numerator
+                m = _RATIONAL_FORMAT.match(input)
+                if m is None:
+                    raise ValueError('Invalid literal for Rational: ' + input)
+                numerator = int(m.group('num'))
+                # Default denominator to 1. That's the only optional group.
+                denominator = int(m.group('denom') or 1)
+                if m.group('sign') == '-':
+                    numerator = -numerator
+
+            elif (not isinstance(numerator, numbers.Integral) and
+                  isinstance(numerator, RationalAbc)):
+                # Handle copies from other rationals.
+                other_rational = numerator
+                numerator = other_rational.numerator
+                denominator = other_rational.denominator
 
         if (not isinstance(numerator, numbers.Integral) or
             not isinstance(denominator, numbers.Integral)):
@@ -107,10 +135,15 @@ class Rational(RationalAbc):
         g = _gcd(numerator, denominator)
         self._numerator = int(numerator // g)
         self._denominator = int(denominator // g)
+        return self
 
     @classmethod
     def from_float(cls, f):
-        """Converts a float to a rational number, exactly."""
+        """Converts a finite float to a rational number, exactly.
+
+        Beware that Rational.from_float(0.3) != Rational(3, 10).
+
+        """
         if not isinstance(f, float):
             raise TypeError("%s.from_float() only takes floats, not %r (%s)" %
                             (cls.__name__, f, type(f).__name__))
@@ -118,6 +151,26 @@ class Rational(RationalAbc):
             raise TypeError("Cannot convert %r to %s." % (f, cls.__name__))
         return cls(*_binary_float_to_ratio(f))
 
+    @classmethod
+    def from_decimal(cls, dec):
+        """Converts a finite Decimal instance to a rational number, exactly."""
+        from decimal import Decimal
+        if not isinstance(dec, Decimal):
+            raise TypeError(
+                "%s.from_decimal() only takes Decimals, not %r (%s)" %
+                (cls.__name__, dec, type(dec).__name__))
+        if not dec.is_finite():
+            # Catches infinities and nans.
+            raise TypeError("Cannot convert %s to %s." % (dec, cls.__name__))
+        sign, digits, exp = dec.as_tuple()
+        digits = int(''.join(map(str, digits)))
+        if sign:
+            digits = -digits
+        if exp >= 0:
+            return cls(digits * 10 ** exp)
+        else:
+            return cls(digits, 10 ** -exp)
+
     @property
     def numerator(a):
         return a._numerator
@@ -128,15 +181,14 @@ class Rational(RationalAbc):
 
     def __repr__(self):
         """repr(self)"""
-        return ('rational.Rational(%r,%r)' %
-                (self.numerator, self.denominator))
+        return ('Rational(%r,%r)' % (self.numerator, self.denominator))
 
     def __str__(self):
         """str(self)"""
         if self.denominator == 1:
             return str(self.numerator)
         else:
-            return '(%s/%s)' % (self.numerator, self.denominator)
+            return '%s/%s' % (self.numerator, self.denominator)
 
     def _operator_fallbacks(monomorphic_operator, fallback_operator):
         """Generates forward and reverse operators given a purely-rational