[Python-checkins] r60344 - in python/trunk/Lib: rational.py test/test_rational.py
jeffrey.yasskin
python-checkins at python.org
Sun Jan 27 06:40:36 CET 2008
Author: jeffrey.yasskin
Date: Sun Jan 27 06:40:35 2008
New Revision: 60344
Modified:
python/trunk/Lib/rational.py
python/trunk/Lib/test/test_rational.py
Log:
Make rational.gcd() public and allow Rational to take decimal strings, per
Raymond's advice.
Modified: python/trunk/Lib/rational.py
==============================================================================
--- python/trunk/Lib/rational.py (original)
+++ python/trunk/Lib/rational.py Sun Jan 27 06:40:35 2008
@@ -14,8 +14,8 @@
RationalAbc = numbers.Rational
-def _gcd(a, b): # XXX This is a useful function. Consider making it public.
- """Calculate the Greatest Common Divisor.
+def gcd(a, b):
+ """Calculate the Greatest Common Divisor of a and b.
Unless b==0, the result will have the same sign as b (so that when
b is divided by it, the result comes out positive).
@@ -40,8 +40,8 @@
>>> _binary_float_to_ratio(-.25)
(-1, 4)
"""
- # XXX Consider moving this to to floatobject.c
- # with a name like float.as_intger_ratio()
+ # XXX Move this to floatobject.c with a name like
+ # float.as_integer_ratio()
if x == 0:
return 0, 1
@@ -80,12 +80,9 @@
_RATIONAL_FORMAT = re.compile(
- r'^\s*(?P<sign>[-+]?)(?P<num>\d+)(?:/(?P<denom>\d+))?\s*$')
+ r'^\s*(?P<sign>[-+]?)(?P<num>\d+)'
+ r'(?:/(?P<denom>\d+)|\.(?P<decimal>\d+))?\s*$')
-# XXX Consider accepting decimal strings as input since they are exact.
-# Rational("2.01") --> s="2.01" ; Rational.from_decimal(Decimal(s)) --> Rational(201, 100)"
-# If you want to avoid going through the decimal module, just parse the string directly:
-# s.partition('.') --> ('2', '.', '01') --> Rational(int('2'+'01'), 10**len('01')) --> Rational(201, 100)
class Rational(RationalAbc):
"""This class implements rational numbers.
@@ -96,7 +93,7 @@
Rational() == 0.
Rationals can also be constructed from strings of the form
- '[-+]?[0-9]+(/[0-9]+)?', optionally surrounded by spaces.
+ '[-+]?[0-9]+((/|.)[0-9]+)?', optionally surrounded by spaces.
"""
@@ -106,7 +103,8 @@
def __new__(cls, numerator=0, denominator=1):
"""Constructs a Rational.
- Takes a string, another Rational, or a numerator/denominator pair.
+ Takes a string like '3/2' or '3.2', another Rational, or a
+ numerator/denominator pair.
"""
self = super(Rational, cls).__new__(cls)
@@ -118,9 +116,18 @@
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)
+ numerator = m.group('num')
+ decimal = m.group('decimal')
+ if decimal:
+ # The literal is a decimal number.
+ numerator = int(numerator + decimal)
+ denominator = 10**len(decimal)
+ else:
+ # The literal is an integer or fraction.
+ numerator = int(numerator)
+ # Default denominator to 1.
+ denominator = int(m.group('denom') or 1)
+
if m.group('sign') == '-':
numerator = -numerator
@@ -139,7 +146,7 @@
if denominator == 0:
raise ZeroDivisionError('Rational(%s, 0)' % numerator)
- g = _gcd(numerator, denominator)
+ g = gcd(numerator, denominator)
self.numerator = int(numerator // g)
self.denominator = int(denominator // g)
return self
Modified: python/trunk/Lib/test/test_rational.py
==============================================================================
--- python/trunk/Lib/test/test_rational.py (original)
+++ python/trunk/Lib/test/test_rational.py Sun Jan 27 06:40:35 2008
@@ -9,10 +9,28 @@
from copy import copy, deepcopy
from cPickle import dumps, loads
R = rational.Rational
+gcd = rational.gcd
+
+
+class GcdTest(unittest.TestCase):
+
+ def testMisc(self):
+ self.assertEquals(0, gcd(0, 0))
+ self.assertEquals(1, gcd(1, 0))
+ self.assertEquals(-1, gcd(-1, 0))
+ self.assertEquals(1, gcd(0, 1))
+ self.assertEquals(-1, gcd(0, -1))
+ self.assertEquals(1, gcd(7, 1))
+ self.assertEquals(-1, gcd(7, -1))
+ self.assertEquals(1, gcd(-23, 15))
+ self.assertEquals(12, gcd(120, 84))
+ self.assertEquals(-12, gcd(84, -120))
+
def _components(r):
return (r.numerator, r.denominator)
+
class RationalTest(unittest.TestCase):
def assertTypedEquals(self, expected, actual):
@@ -55,8 +73,12 @@
self.assertEquals((3, 2), _components(R("3/2")))
self.assertEquals((3, 2), _components(R(" \n +3/2")))
self.assertEquals((-3, 2), _components(R("-3/2 ")))
- self.assertEquals((3, 2), _components(R(" 03/02 \n ")))
- self.assertEquals((3, 2), _components(R(u" 03/02 \n ")))
+ self.assertEquals((13, 2), _components(R(" 013/02 \n ")))
+ self.assertEquals((13, 2), _components(R(u" 013/02 \n ")))
+
+ self.assertEquals((16, 5), _components(R(" 3.2 ")))
+ self.assertEquals((-16, 5), _components(R(u" -3.2 ")))
+
self.assertRaisesMessage(
ZeroDivisionError, "Rational(3, 0)",
@@ -76,9 +98,21 @@
ValueError, "Invalid literal for Rational: + 3/2",
R, "+ 3/2")
self.assertRaisesMessage(
- # Only parse fractions, not decimals.
- ValueError, "Invalid literal for Rational: 3.2",
- R, "3.2")
+ # Avoid treating '.' as a regex special character.
+ ValueError, "Invalid literal for Rational: 3a2",
+ R, "3a2")
+ self.assertRaisesMessage(
+ # Only parse ordinary decimals, not scientific form.
+ ValueError, "Invalid literal for Rational: 3.2e4",
+ R, "3.2e4")
+ self.assertRaisesMessage(
+ # Don't accept combinations of decimals and rationals.
+ ValueError, "Invalid literal for Rational: 3/7.2",
+ R, "3/7.2")
+ self.assertRaisesMessage(
+ # Don't accept combinations of decimals and rationals.
+ ValueError, "Invalid literal for Rational: 3.2/7",
+ R, "3.2/7")
def testImmutable(self):
r = R(7, 3)
@@ -368,7 +402,7 @@
self.assertEqual(id(r), id(deepcopy(r)))
def test_main():
- run_unittest(RationalTest)
+ run_unittest(RationalTest, GcdTest)
if __name__ == '__main__':
test_main()
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