Python3.2官方文档翻译-列表工具和十进制浮点数计算

Python3.2官方文档翻译-列表工具和十进制浮点数计算

8.7 列表工具

许多数据结构需求能通过内置列表类型满足，但是，有时处于不同性能取舍需要从中选择一种实现。

Array模块能提供一个像列表的array对象，它仅仅能存储同类数据并且更加简洁。接下来例子展示了一个数字数组。存储是2个字节的无标识的二进制数据而不是在python对象中普通列表中的每个16字节的值。

>>> from array import array

>>> a = array(’H’, [4000, 10, 700, 22222])

>>> sum(a)

26932

>>> a[1:3]

array(’H’, [10, 700])

Collections模块通过方法depue（）提供了一个类似列表对象，它从左边开始能更加快速添加和删除，但是在中间查询时很慢。这些对象很适合实现队列和广度优先查询。

除了代替列表实现之外，标准库还提供了其他工具，比如处理排序列表的bisect模块。

>>> import bisect<喎?http://www.Bkjia.com/kf/ware/vc/" target="_blank" class="keylink">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"http://www.2cto.com/uploadfile/Collfiles/20140519/20140519090801164.jpg" alt="">

Decimal模块为算术运算提供了高精度的需要

>>> from decimal import*

>>> round(Decimal(’0.70’)*Decimal(’1.05’), 2)

Decimal(’0.74’)

>>> round(.70*1.05, 2) 0.73