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Jul 4, 2008, 12:36 PM
Post #1 of 2
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[issue3285] Fraction.from_any()
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New submission from Raymond Hettinger <rhettinger [at] users>:
After exercising the fractions module, I've found it problematic that
there isn't a unified constructor to handle mixed data input types.
For example, when updating the accurate summation recipe at
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/393090 to show
how it could be done with rational arithmetic. Handling mixed-type
inputs required writing a factory function:
def makefrac(x):
if isinstance(x, Decimal):
return Fraction.from_decimal(x)
if isinstance(x, float):
return Fraction.from_float(x)
return Fraction(x)
That function supported a clean version of the recipe:
def frsum(iterable):
return float(sum(map(makefrac, iterable)))
It would have been much better if that functionality were built into
the class definition. See attached patch.
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components: Library (Lib)
files: from_any.diff
keywords: patch
messages: 69264
nosy: rhettinger
severity: normal
status: open
title: Fraction.from_any()
type: feature request
versions: Python 2.6, Python 3.0
Added file: http://bugs.python.org/file10810/from_any.diff
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<http://bugs.python.org/issue3285>
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