I create a list of lists and want to append items to the individual lists, but when I try to append to one of the lists (a[0].append(2)), the item gets added to all lists.
a = []
b = [1]
a.append(b)
a.append(b)
a[0].append(2)
a[1].append(3)
print(a)
Gives: [[1, 2, 3], [1, 2, 3]]
Whereas I would expect: [[1, 2], [1, 3]]
Changing the way I construct the initial list of lists, making b a float instead of a list and putting the brackets inside .append(), gives me the desired output:
a = []
b = 1
a.append([b])
a.append([b])
a[0].append(2)
a[1].append(3)
print(a)
Gives: [[1, 2], [1, 3]]
But why? It is not intuitive that the result should be different. I know this has to do with there being multiple references to the same list, but I don't see where that is happening.