乘以相同字典的键答案

【问题标题】：Multiply key of the same dict乘以相同字典的键
【发布时间】：2017-03-27 07:04:40
【问题描述】：

我使用的是 python 3.5，我需要乘以这个字典，这应该输出字典每个键的乘法结果。

{0: [0.0008726003490401396, 0.004363001745200698, 0.0008726003490401396, 0.0008726003490401396, 0.0017452006980802793, 0.008726003490401396, 0.0008726003490401396, 0.0017452006980802793, 0.0008726003490401396, 0.0017452006980802793, 0.0017452006980802793, 0.0008726003490401396, 0.0008726003490401396], 1: [0.007853403141361256, 0.008726003490401396, 0.0008726003490401396], 2: [0.004363001745200698, 0.0008726003490401396, 0.0008726003490401396, 0.0017452006980802793, 0.0008726003490401396, 0.0008726003490401396, 0.007853403141361256, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.002617801047120419, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0017452006980802793, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0017452006980802793, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.002617801047120419, 0.0008726003490401396, 0.0008726003490401396, 0.0017452006980802793, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.002617801047120419, 0.0034904013961605585, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.002617801047120419, 0.0008726003490401396, 0.0034904013961605585, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396, 0.0008726003490401396]}

这是我的尝试，但不起作用：

lista = {k: [v*v for v in v] for k, v in lista.items()}

我会输出例如：

{0: [0.068726003490401396], 1: [0.077853403141361256, 2: [0.098363001745200698]}

【问题讨论】：

查看python的'reduce'函数，而不是内部列表理解

标签： python python-3.x dictionary list-comprehension dict-comprehension

【解决方案1】：

使用字典理解和functools.reduce + operator.mul：

>>> from functools import mul
>>> mul(3, 4)  # == 3 * 4
12

>>> from functools import reduce
>>> reduce(mul, [3, 4, 2])  # == (3 * 4) * 2
24

>>> from functools import reduce
>>> from operator import mul
>>>
>>> lista = {
...     0: [0.0008726003490401396, 0.004363001745200698],
...     1: [0.007853403141361256, 0.008726003490401396, 0.0008726003490401396],
...     2: [0.004363001745200698, 0.0008726003490401396, 0.0008726003490401396],
... }
>>>
>>> {key: reduce(mul, value) for key, value in lista.items()}
{0: 3.8071568457248673e-06, 1: 5.979827506374137e-08, 2: 3.322126392430076e-09}
>>> {key: [reduce(mul, value)] for key, value in lista.items()}
{0: [3.8071568457248673e-06], 1: [5.979827506374137e-08], 2: [3.322126392430076e-09]}

【讨论】：

感谢您的回答..但是 0.0008726003490401396*0.004363001745200698= 不是蜕皮的结果..
@DavideDiMenna，那么，您能否详细说明预期值是如何计算的？
你是对的人！现在我尝试这样做.. 不是没有进口的方法吗？
@DavideDiMenna，您可以将mul 替换为lambda a, b: a * b。但 reduce 应该在 Python 3.x 中导入。
@DavideDiMenna, reduce(..) -> reduce(..) * 0.5 似乎是你想要的。