3D Numpy Array Nested Loop Python

Question

I wanted to learn a little bit more the handling of numpy arrays. I would like to have a nested loop through a 3D numpy array.

The result should look like:

2017-11-11, 1859
2017-11-12, 1359

I want would like to have as described as nested loop. My current loop looks like the following:

class Calculates(object):    
    def __init__(self, x, y):
        self.x = x
        self.y = y        
    def Calculator(self):
        calc = self.x*self.y

        return calc

playground = [['2017-11-11', 18, 17],
              ['2017-11-11', 16, 19],
              ['2017-11-11', 16, 19],
              ['2017-11-11', 20, 24],
              ['2017-11-11', 31, 15],
              ['2017-11-12', 10, 4],
              ['2017-11-12', 12, 3],
              ['2017-11-12', 15, 67],
              ['2017-11-12', 12, 23],
              ['2017-11-12', 1, 2]]   

for date, x, y in playground:
    print(date)
    calc = Calculates(x,y).Calculator()
    print(calc)

With this code I receive:

I would like to have it in such a way for the for loop:

for date in playground:
    print(date)
    for x,y in playground:
        calc = Calculates(x,y).Calculator()
        print(calc)

to get the results described above.

but receive the following error message:

ValueError: too many values to unpack (expected 2)

akuiper · Accepted Answer · 2018-02-04 23:04:43Z

1

You need to multiply values from the same date together and add them up; One way to do this is to aggregate the result using a dictionary with date as the key; here is an example using a defaultdict with zero as the default value:

from collections import defaultdict

# aggregate the result into d
d = defaultdict(int)

for date, x, y in playground:    
    calc = Calculates(x,y).Calculator()
    d[date] += calc

# print the dictionary
for date, calc in d.items():
    print(date, calc)
# 2017-11-11 1859
# 2017-11-12 1359

edited Feb 4, 2018 at 23:04

answered Feb 4, 2018 at 22:51

akuiper

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