On 24/03/2016 14:08, Jon Ribbens wrote:
On 2016-03-24, BartC <b...@freeuk.com> wrote:
On 24/03/2016 13:50, Steven D'Aprano wrote:
Likewise clearing a list:
for i in range(len(mylist)-1, -1, 0):
del mylist[i]
That's wouldn't be I'd call clearing a list, more like destroying it
completely!
How would you actually clear a list by traversing it (ie. not just
building a new one)?
This doesn't work:
for x in L:
x=0
as each x only refers to the value in each element of L, not the element
itself (like the pass-by-reference problem).
I'd presumably have to do:
for i in range(len(L)):
L[i]=0
That's kind've a weird thing to want to do;
The thing I'm trying to demonstrate is changing an element of a list
that you are traversing in a loop. Not necessarily set all elements to
the same value.
if you thought you needed
to do that then most likely what you should actually be doing is
re-writing your code so you no longer need to. However, you could do:
L[:] = [0] * len(L)
OK, but that's just building a new list as I've already mentioned.
Or is the Pythonic way, when you want to change some elements of a list
to just build a new one that incorporates those changes?
--
Bartc
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