fractions — 有理数 ¶

源代码： Lib/fractions.py

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The fractions 模块提供有理数算术支持。

Fraction 实例可以构造自一对整数、另一有理数或字符串。

class fractions. Fraction ( numerator = 0 , denominator = 1 ) ¶

class fractions. Fraction ( other_fraction )

class fractions. Fraction ( float )

class fractions. Fraction ( decimal )

class fractions. Fraction ( string )

第 1 个版本要求 numerator and denominator 是实例化的 numbers.Rational 并返回新的 Fraction 实例采用值 numerator/denominator 。若 denominator is 0 ，引发 ZeroDivisionError 。第 2 个版本要求 other_fraction 是实例化的 numbers.Rational 并返回 Fraction instance with the same value. The next two versions accept either a float 或 decimal.Decimal instance, and return a Fraction instance with exactly the same value. Note that due to the usual issues with binary floating point (see 浮点算术：问题和局限性 ), the argument to Fraction(1.1) is not exactly equal to 11/10, and so Fraction(1.1) does not return Fraction(11, 10) as one might expect. (But see the documentation for the limit_denominator() method below.) The last version of the constructor expects a string or unicode instance. The usual form for this instance is:

[sign] numerator ['/' denominator]