Davide Di Menna Davide Di Menna - 19 days ago 4
Python Question

Multiply key of the same dict

I'm using python 3.5,
I need to multiply this dict and this should output the result of multiplication of each key of dict.

{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]}


This is my try but does not work:

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


the output i would is for example:

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

Answer

Using dictionary comprehension and 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]}
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