brw59 brw59 - 7 months ago 24
Python Question

append tuples to array in groups python

I'm trying to append tuples to my array in groups. The number of groups or the number of tuples in each group is unknown.

I'm aware there should be a very simple answer for this, but my mind is grasped on swift, which takes care of this issue for me.

This is my issue, I need to be able to do this:

array = []
array[0].append([1, 2]) # error because there isn't a '0' index
array[0].append([7, 2])
array[0].append([89, -5])
array[1].append([2, 3])


so I don't get the wrong kind of responses of why I'm not doing it another way I made a simple program to illustrate the point of why I need it to work like this.

def get_data(index, array):
# loop for an un-determined number of times, calculates differently depending on the index
one_or_more = 4
for i in range(0, one_or_more):
# do some calculations depending on index, which should differ for each loop
data1 = index * 3 + i
data2 = index * 4 + i
array.append([data1, data2])


def main():

array = []
array_index = 0
some_num = "110, 121, 122, 123, 124, 125, 130, 131, 323, 324, 325, 326, 340, 341, 342, 343".strip().split(", ")
for i in some_num:
get_data(int(i), array[array_index]) # error here with 'array[array_index]', because I can't index array with '0' because it's not initialized yet
array_index += 1

if __name__ == "__main__":main()

Answer

The value at a given index is being over written. So, an array is not a suitable data structure for your task. I would use a defaultdict.

from collections import defaultdict

key_lists = defaultdict(list)
key_lists[0].append([1,2])
key_lists[0].append([89, -5])
key_lists[1].append([2, 3])

print(key_lists)
print(key_lists[0])

one_or_more = 4

for i in range(0, one_or_more):
    data1 = index * 3 + i
    data2 = index * 4 + i
    key_lists[i].append([data1, data2]