Removing items from a list in a loop

[Bjorn Pettersen]

"Thaddeus L. Olczyk" wrote:
> 
> I would like to remove a bunch of items from a list *efficiently*.
> Essentially  I would like to do this:
> 
>    for x in list:
>         if Function(x):
>         list.remove(x)
> 
> This does not work. Presumably for this reason:
[snip]

the obvious way:

  for x in list[:]:  # create a copy
    if f(x):
      list.remove(x)

perhaps faster:

  for i in range(len(list)-1, 0, -1):
    x = list[i]
    if f(x):
      list.remove(x)

that traverses the list backwards, so should be more resistant to the
list changing...

-- bjorn