How can I convert a list of strings (each entry is three numbers separated by spaces) to an array of numbers?

Edited for clarity
Let’s say I have a list like this:
[‘1, 2, 3’, ‘4, 5, 6’, ‘7, 8, 9’]
wherein each entry is one string of 3 numbers.

How would I get this list into an array (of floats), such that 1, 4, and 7 correspond to the first column; 2, 5, and 8 correspond to the second column; and 3, 6, 9 are in the last column?

I’ve searched through other questions, most of which aren’t quite answering my particular question.

arr =  ['1, 2, 3', '4, 5, 6', '7, 8, 9']
new_arr = [[],[],[]]

for column in arr:
    column = column.split(", ")
    new_arr[0].append(float(column[0]))
    new_arr[1].append(float(column[1]))
    new_arr[2].append(float(column[2]))

print(new_arr)
#prints [[1.0, 4.0, 7.0], [2.0, 5.0, 8.0], [3.0, 6.0, 9.0]]