On 15/06/21 7:32 pm, Jach Feng wrote:
But usually the list creation is not in simple way:-) for example:
a = [1,2]
m = [a for i in range(3)]
m
[[1, 2], [1, 2], [1, 2]]
id(m[0]) == id(m[1]) == id(m[2])
True
The first line is only executed once, so you just get one
list object [1, 2]. You then refer to that object three times
when you build the outer list.
To get three different [1, 2] lists you would need something
like this:
m = [[1,2] for i in range(3)]
This executes the [1, 2] expression 3 times. Because lists are
mutable, you can be sure that this will give you 3 distinct
list objects.
--
Greg
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