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diff --git a/Doc/library/fractions.rst b/Doc/library/fractions.rst new file mode 100644 index 0000000..af6ed76 --- /dev/null +++ b/Doc/library/fractions.rst @@ -0,0 +1,75 @@ + +:mod:`fractions` --- Rational numbers +==================================== + +.. module:: fractions + :synopsis: Rational numbers. +.. moduleauthor:: Jeffrey Yasskin <jyasskin at gmail.com> +.. sectionauthor:: Jeffrey Yasskin <jyasskin at gmail.com> +.. versionadded:: 2.6 + + +The :mod:`fractions` module defines an immutable, infinite-precision +Fraction number class. + + +.. class:: Fraction(numerator=0, denominator=1) + Fraction(other_fraction) + Fraction(string) + + The first version requires that *numerator* and *denominator* are + instances of :class:`numbers.Integral` and returns a new + ``Fraction`` representing ``numerator/denominator``. If + *denominator* is :const:`0`, raises a :exc:`ZeroDivisionError`. The + second version requires that *other_fraction* is an instance of + :class:`numbers.Rational` and returns an instance of + :class:`Fraction` with the same value. The third version expects a + string of the form ``[-+]?[0-9]+(/[0-9]+)?``, optionally surrounded + by spaces. + + Implements all of the methods and operations from + :class:`numbers.Rational` and is immutable and hashable. + + +.. method:: Fraction.from_float(flt) + + This classmethod constructs a :class:`Fraction` representing the + exact value of *flt*, which must be a :class:`float`. Beware that + ``Fraction.from_float(0.3)`` is not the same value as ``Fraction(3, + 10)`` + + +.. method:: Fraction.from_decimal(dec) + + This classmethod constructs a :class:`Fraction` representing the + exact value of *dec*, which must be a + :class:`decimal.Decimal`. + + +.. method:: Fraction.__floor__() + + Returns the greatest :class:`int` ``<= self``. Will be accessible + through :func:`math.floor` in Py3k. + + +.. method:: Fraction.__ceil__() + + Returns the least :class:`int` ``>= self``. Will be accessible + through :func:`math.ceil` in Py3k. + + +.. method:: Fraction.__round__() + Fraction.__round__(ndigits) + + The first version returns the nearest :class:`int` to ``self``, + rounding half to even. The second version rounds ``self`` to the + nearest multiple of ``Fraction(1, 10**ndigits)`` (logically, if + ``ndigits`` is negative), again rounding half toward even. Will be + accessible through :func:`round` in Py3k. + + +.. seealso:: + + Module :mod:`numbers` + The abstract base classes making up the numeric tower. + |