diff options
Diffstat (limited to 'Lib/rational.py')
| -rwxr-xr-x | Lib/rational.py | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/Lib/rational.py b/Lib/rational.py index 89b622c..da75ab1 100755 --- a/Lib/rational.py +++ b/Lib/rational.py @@ -13,8 +13,8 @@ __all__ = ["Rational"] 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). @@ -39,8 +39,8 @@ def _binary_float_to_ratio(x): >>> _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 @@ -79,12 +79,9 @@ def _binary_float_to_ratio(x): _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. @@ -95,7 +92,7 @@ class Rational(RationalAbc): 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. """ @@ -105,7 +102,8 @@ class Rational(RationalAbc): 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 '1.5', another Rational, or a + numerator/denominator pair. """ self = super(Rational, cls).__new__(cls) @@ -117,9 +115,18 @@ class Rational(RationalAbc): 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 @@ -138,7 +145,7 @@ class Rational(RationalAbc): 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 |