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Diffstat (limited to 'Doc/library/fractions.rst')
| -rw-r--r-- | Doc/library/fractions.rst | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/Doc/library/fractions.rst b/Doc/library/fractions.rst index 1deea64..9ef1230 100644 --- a/Doc/library/fractions.rst +++ b/Doc/library/fractions.rst @@ -46,6 +46,24 @@ Rational number class. :class:`decimal.Decimal`. +.. method:: Fraction.limit_denominator(max_denominator=1000000) + + Finds and returns the closest :class:`Fraction` to ``self`` that + has denominator at most max_denominator. This method is useful for + finding rational approximations to a given floating-point number:: + + >>> Fraction('3.1415926535897932').limit_denominator(1000) + Fraction(355, 113) + + or for recovering a rational number that's represented as a float:: + + >>> from math import pi, cos + >>> Fraction.from_float(cos(pi/3)) + Fraction(4503599627370497L, 9007199254740992L) + >>> Fraction.from_float(cos(pi/3)).limit_denominator() + Fraction(1, 2) + + .. method:: Fraction.__floor__() Returns the greatest :class:`int` ``<= self``. Will be accessible |