What happened when I wrote "a, b, c = [[],] * 3" in python? It seems that a, b, c are the same object

Question

What happened when I wrote a, b, c = [[],] * 3 in python?
It seems that a, b, c are the same object.

a, b, c = [[],] * 3
a.append(1)
b.append(2)
print(c)

The answer is [1,2] , why?

score -2 · Accepted Answer · answered Sep 12 '19 at 08:33

-2

The * operator just creates copies of the same list [] three times, not three fresh lists.

So, a, b, c all point to the same list. And you added 1 and 2 to both.

This:

a, b, c = [[] for _ in range(3)]
a.append(1)
b.append(2)
print(c)

would give you [] as expected.

answered Sep 12 '19 at 08:33

Saswat Padhi

copy of object mean, creating a altogether new object with same value. in this case it's not copy it's is reference, 3 object are created which are referenced to same object – sahasrara62 Sep 12 '19 at 08:42
It **is** a copy of the pointer! – Saswat Padhi Sep 12 '19 at 08:49
There is no such thing as a "reference". The underlying semantics is that of copying pointers -- which point to the same memory location. – Saswat Padhi Sep 12 '19 at 08:52

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