How to combine multiple numpy arrays into a dictionary list

Question

I have the following array:

column_names = ['id', 'temperature', 'price']

And three numpy array as follows:

idArry = ([1,2,3,4,....])

tempArry = ([20.3,30.4,50.4,.....])

priceArry = ([1.2,3.5,2.3,.....])

I wanted to combine the above into a dictionary as follows:

table_dict = ( {'id':1, 'temperature':20.3, 'price':1.2 },
               {'id':2, 'temperature':30.4, 'price':3.5},...)

I can use a for loop together with append to create the dictionary but the list is huge at about 15000 rows. Can someone show me how to use python zip functionality or other more efficient and fast way to achieve the above requirement?

Answer 1

You can use a listcomp and the function zip():

[{'id': i, 'temperature': j, 'price': k} for i, j, k in zip(idArry, tempArry, priceArry)]
# [{'id': 1, 'temperature': 20.3, 'price': 1.2}, {'id': 2, 'temperature': 30.4, 'price': 3.5}]

If your ids are 1, 2, 3... and you use a list you don’t need ids in your dicts. This is a redundant information in the list.

[{'temperature': i, 'price': j} for i, j in zip(tempArry, priceArry)]

You can use also a dict of dicts. The lookup in the dict must be faster than in the list.

{i: {'temperature': j, 'price': k} for i, j, k in zip(idArry, tempArry, priceArry)}
# {1: {'temperature': 20.3, 'price': 1.2}, 2: {'temperature': 30.4, 'price': 3.5}}