List replication operator

[Steven D'Aprano]

Python has a sequence replication operator:

py> [1, 2]*3
[1, 2, 1, 2, 1, 2]


Unfortunately, it is prone to a common "gotcha":

py> x = [[]]*5  # make a multi-dimensional list
py> x
[[], [], [], [], []]
py> x[0].append(1)
py> x
[[1], [1], [1], [1], [1]]


The reason for this behaviour is that * does not copy the original list's 
items, it simply replicates the references to the items. So we end up 
with a new list containing five references to the same inner list.


This is not a bug and changing the behaviour is not an option.

But what do people think about proposing a new list replication with copy 
operator?

    [[]]**5

would return a new list consisting of five shallow copies of the inner 
list.


Thoughts?



-- 
Steve