On 1/13/2014 4:00 AM, Laszlo Nagy wrote:
Unless L is aliased, this is silly code.
There is another use case. If you intend to modify a list within a for
loop that goes over the same list, then you need to iterate over a copy.
And this cannot be called an "alias" because it has no name:
for i in somelist: creates a second reference to somelist that somewhere
in the loop code has a name, so it is effectively an 'alias'. The
essential point is that there are two access paths to the same object.
for idx,item in enumerate(L[:]):
# do something with L here, including modification
The copy is only needed in the above if one inserts or deletes. But if
one inserts or deletes more than one item, one nearly always does better
to iterate through the original and construct a new list with new items
added and old items not copied.
--
Terry Jan Reedy
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