但是
>>> import decimal

Traceback (most recent call last):
  File "", line 1, in -toplevel-
    import decimal
ImportError: No module named decimal

On 7/11/06, Bing Yuan <aceyuan在gmail.com> wrote:
> 引自shhgs的帖子"Py2.5 What's new 之 with" （搜索前贴能找到）
> ==================================================
> ...
> decimal模块提供了一个能返回context对象的con
> text_manager()方法(请注意看注释，
> 至少Py2.5b1里面是没有这个方法，你得用get_manager() )，这个context对象
> (context是上下文的意思)将计算的精度和近似要求封装了起来
> (什么叫上下文？这才叫上下文！Perl的那个上下文根本就是假冒伪劣):
>
> import decimal
>
> # Displays with default precision of 28 digits
> v1 = decimal.Decimal('578')
> print v1.sqrt()
>
> ctx = decimal.Context(prec=16)
> #----------------------------------------
> # 根据shhgs的试验，ctx对象是没有context_manager()方法的，
> # 你得
> # with ctx.get_manager() :
> #----------------------------------------
> with ctx.context_manager():
>    # All code in this block uses a precision of 16 digits.
>    # The original context is restored on exiting the block.
>    print v1.sqrt()
> ...
> ===========================================
>
>
> On 7/9/06, shhgs <shhgs.efhilt在gmail.com> wrote:
> > import decimal
> >
> > On 7/9/06, swordsp <sparas2006在gmail.com> wrote:
> > > 十进制数在python内部都是通过二进制数表达的，所以"不存在"0.833这样一个float数值：
> > > >>> 0.833
> > > 0.83299999999999996
> > > 这就是python内部float所能表达的最接近0.833的值。
> > >
> > >
> 如果你一定需要0.833（我觉得绝大多数时候其实并没有这个需求），就不能使用内建的float，要用别的自定义类型。
> > >
> > >
> > >  On 7/9/06, linda. s < samrobertsmith在gmail.com> wrote:
> > > > 变成string了,如果我还是想要float,但同时想限制小数点?
> > > >
> > > > On 7/9/06, Zoom. Quiet <zoom.quiet在gmail.com> wrote:
> > > > > On 7/9/06, linda. s < samrobertsmith在gmail.com > wrote:
> > > > > > 怎么限制小数点,
> > > > > > 比如说
> > > > > > >>> 5/6.
> > > > > > 0.83333333333333337
> > > > > >
> > > > > >>> "%.3f"%(5/6.0)
> > > > > '0.833'
> > > > >
> > > > > > 我想就要0.83
> > > > > >
> > > >
> > > >
> > >
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On 9/13/06, linda. s <samrobertsmith在gmail.com> wrote:
> 但是
> >>> import decimal
>
> Traceback (most recent call last):
>   File "", line 1, in -toplevel-
>     import decimal
> ImportError: No module named decimal
>
decimal是2.4中才有的。

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同意swordsp所说的"不存在"0.833这样一个float数值。
这应该是计算机的基础知识吧。如果想要0.833，只有自己在转换了。

2006/9/13, limodou <limodou在gmail.com>:
> On 9/13/06, linda. s <samrobertsmith在gmail.com> wrote:
> > 但是
> > >>> import decimal
> >
> > Traceback (most recent call last):
> >   File "", line 1, in -toplevel-
> >     import decimal
> > ImportError: No module named decimal
> >
> decimal是2.4中才有的。
>
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