How to rewrite this as list comprehension?

[Paul Moore]

On Tue, 19 Dec 2000 13:07:49 +0100, "Serge Beaumont"
<serge at sergebeaumont.com> wrote:

>Hello,
>
>I'm trying to get my head around comprehensions. How would I rewrite this
>method?
>
>  def deadThings(self, type = None):
>    deadThings = self.destroyed[:]
>    for thing in self.things:
>      if thing.destroyed:
>        if type:
>          if isinstance(thing, type):
>            deadThings.append(thing)
>        else:
>          deadThings.append(thing)
>    return deadThings

I think it goes:

deadThings = self.destroyed[:]
deadThings += [x for x in self.things
                 if (x.destroyed and
                    (not type or isinstance(x, type)))]

Start from the inside and work out. The nasty (not type or ...) bit is
a translation of the "if type: if isinstance(): else:" bit into an
expression as opposed to a statement. In C I might have written
    (type ? isinstance() : true)
but I'm not sure it's much clearer.

Whether you find the list comprehension clearer is a matter of taste.
Just because it exists, doesn't mean it is the right answer in all
cases...

Paul