Python list multiply and index-CodePudding

I create 3 empty list nested in a list, and index to append to the first one, but it results in all the list:

In [1]:
   ...: a = [[]] * 3
   ...: a[0].append(3)
   ...: print(a)

Out [1]:
[[3], [3], [3]]

My expect output is:

[[3], [], []]

But if I do this:

In [2]:
   ...: b = []
   ...: for i in range(3):
   ...: b.append([])
   ...: b[0].append(3)
   ...: print(b)

Out [2]:
    [[3], [], []]

Then I got my expect output

Thanks

CodePudding user response：

Because in the first case, you are trying to access the same object (the object and its refernces).

But in the second case, list a has totally different -new- objects.