decouple copy of a list

[cassiope]

On Dec 10, 6:06 am, Jean-Michel Pichavant <jeanmic... at sequans.com>
wrote:
> Dirk Nachbar wrote:
> > I want to take a copy of a list a
>
> > b=a
>
> > and then do things with b which don't affect a.
>
> > How can I do this?
>
> > Dirk
>
> In [1]: a = [1,2,3]
>
> In [2]: b = a[:]
>
> In [3]: b[0] = 5
>
> In [4]: a
> Out[4]: [1, 2, 3]
>
> In [5]: b
> Out[5]: [5, 2, 3]
>
> Alternatively, you can write
>
> import copy
> a = [1,2,3]
> b = a.copy()
>
> if the list a contains mutable objects, use copy.deepcopy
> (http://docs.python.org/library/copy.html)
>
> JM

I'm not a pyguru, but... you didn't use copy quite right.
Try instead: b= copy.copy(a)

The other issue that the original person has noticed is that
a list may include a reference to something.  When a list is
copied - if the reference is copied (not "deepcopied"], changes
to the referred object will be visible in both lists, even if
they are different lists.

For more information, refer to the docs in the <copy> module.

HTH...