Gabriel a écrit :
Hi all
Just wondering if someone could clarify this behaviour for me, please?
tasks = [[]]*6
tasks
[[], [], [], [], [], []]
tasks[0].append(1)
tasks
[[1], [1], [1], [1], [1], [1]]
Well what I was expecting to end up with was something like:
>>> tasks
[[1], [], [], [], [], []]
The problem here is that your first statement
#>>> tasks = [[]]*6
creates a list (task) containing 6 references to the *same* (empty) list
object. You can check this easily using the identity test operator 'is':
#>>> tasks[0] is tasks[1]
True
In fact, it's exactly as if you had written:
#>>> task = []
#>>> tasks = []
#>>> for i in range(6):
#... tasks.append(task)
#...
If you want 6 different list objects in tasks, you can use a list
comprehension instead:
#>>> tasks = [[] for i in range(6)]
#>>> tasks
[[], [], [], [], [], []]
#>>> tasks[0].append(1)
#>>> tasks
[[1], [], [], [], [], []]
HTH
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