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:

 2017-11-11 306 2017-11-11 304 2017-11-11 304 2017-11-11 480 2017-11-11 465 2017-11-12 40 2017-11-12 36 2017-11-12 1005 2017-11-12 276 2017-11-12 2 

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)

Answer 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