what does 'a=b=c=[]' do

[Thomas Rachel]

Am 21.12.2011 23:25 schrieb Eric:

> Is it true that if I want to create an array or arbitrary size such
> as:
>     for a in range(n):
>        x.append(<some function...>)
>
> I must do this instead?
>     x=[]
>     for a in range(n):
>        x.append(<some function...>)

Of course - your x must exist before using it.

 > Now to my actual question.  I need to do the above for multiple arrays
> (all the same, arbitrary size).  So I do this:
>     x=y=z=[]
>     for a in range(n):
>        x.append(<some function...>)
>        y.append(<some other function...>)
>        z.append(<yet another function...>)
> Also, is there a more pythonic way to do "x=[], y=[], z=[]"?

You could do:

def create_xyz(n):
     for a in range(n):
         yield <some function...>, <some other function...>, \
		<yet another function...>)

x, y, z = zip(*create_xyz(11))

or, if you want x, y, z to be lists,

x, y, z = [list(i) for i in zip(*create_xyz(11))]

.


Thomas