Python: Mapping dictionary over multiple np.arrays

Question

How do i map a dictionary over lists of np.ndarrays?

I have a dictionary containing a range of keys and values. It looks something like this:

{1: 0.5,
 2: 0.51,
 3: 0.34,
 4: 0.38,
 5: 0.4,
 6: 0.27,}

In addition, i have a list object containing a range of numpy arrays which looks like this:

[array([1,2,3]),
 array([4,3,5,6]),
 array([1,4,6,2,3])]

I want to map the dictionary over the arrays to replace each value in each array with its corresponding key value in the dictionary. It will yield something like this:

[array([0.5,0.51,0.34]),
 array([0.38,0.34,0.4,0.27]),
 array([0.5,0.38,0.27,0.51,0.34])]

Finally i want to take the mean of each array in the above structure and append this value to a data frame.

Any suggestions?

Have you tried anything yet?

Kasravnd
– Kasravnd

2018-02-12 12:20:30 +00:00
Commented Feb 12, 2018 at 12:20 — Kasravnd
– Kasravnd, Commented Feb 12, 2018 at 12:20

jpp · Accepted Answer · 2018-02-12 12:23:52Z

1

This is one solution.

import numpy as np

d = {1: 0.5,
 2: 0.51,
 3: 0.34,
 4: 0.38,
 5: 0.4,
 6: 0.27,}

lst = [np.array([1,2,3]),
 np.array([4,3,5,6]),
 np.array([1,4,6,2,3])]

lst2 = list(map(np.vectorize(d.get), lst))

# [array([ 0.5 ,  0.51,  0.34]),
#  array([ 0.38,  0.34,  0.4 ,  0.27]),
#  array([ 0.5 ,  0.38,  0.27,  0.51,  0.34])]

answered Feb 12, 2018 at 12:23

jpp

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2 Comments

Jonathan Marin Over a year ago

Perfect! it worked! How do i go from here if i want to get the sum of each array?

jpp Over a year ago

list(map(np.sum, lst)) should work. But if you have more questions, please update your original question / ask a new one. This way SO is useful to a wider audience. If this answer works, feel free to accept (tick on left).

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