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Issue #5812: Make Fraction('1e6') valid. The Fraction constructor now

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accepts all strings accepted by the float and Decimal constructors,
with the exception of strings representing NaNs or infinities.
This commit is contained in:
Mark Dickinson 2009-04-22 17:50:21 +00:00
parent 937491d1a9
commit cf63f2fb88
4 changed files with 47 additions and 33 deletions
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45
Lib/fractions.py
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@ -28,13 +28,14 @@ _RATIONAL_FORMAT = re.compile(r"""
(?P<sign>[-+]?) # an optional sign, then
(?=\d|\.\d) # lookahead for digit or .digit
(?P<num>\d*) # numerator (possibly empty)
(?: # followed by an optional
/(?P<denom>\d+) # / and denominator
(?: # followed by
(?:/(?P<denom>\d+))? # an optional denominator
| # or
\.(?P<decimal>\d*) # decimal point and fractional part
)?
(?:\.(?P<decimal>\d*))? # an optional fractional part
(?:E(?P<exp>[-+]?\d+))? # and optional exponent
)
\s*\Z # and optional whitespace to finish
""", re.VERBOSE)
""", re.VERBOSE | re.IGNORECASE)
class Fraction(numbers.Rational):
@ -65,22 +66,28 @@ class Fraction(numbers.Rational):
if not isinstance(numerator, int) and denominator == 1:
if isinstance(numerator, str):
# Handle construction from strings.
input = numerator
m = _RATIONAL_FORMAT.match(input)
m = _RATIONAL_FORMAT.match(numerator)
if m is None:
raise ValueError('Invalid literal for Fraction: %r' % input)
numerator = m.group('num')
decimal = m.group('decimal')
if decimal:
# The literal is a decimal number.
numerator = int(numerator + decimal)
denominator = 10**len(decimal)
raise ValueError('Invalid literal for Fraction: %r' %
numerator)
numerator = int(m.group('num') or '0')
denom = m.group('denom')
if denom:
denominator = int(denom)
else:
# The literal is an integer or fraction.
numerator = int(numerator)
# Default denominator to 1.
denominator = int(m.group('denom') or 1)
denominator = 1
decimal = m.group('decimal')
if decimal:
scale = 10**len(decimal)
numerator = numerator * scale + int(decimal)
denominator *= scale
exp = m.group('exp')
if exp:
exp = int(exp)
if exp >= 0:
numerator *= 10**exp
else:
denominator *= 10**-exp
if m.group('sign') == '-':
numerator = -numerator