[Tutor] list to string and string to list

[Kent Johnson]

On Thu, Apr 16, 2009 at 6:52 PM, johnf <jfabiani at yolo.com> wrote:
> I am dealing with a database field that can only store strings.
> I want to save the list to the field and when I retrieve the string convert it
> back to a list.
>
> But this does NOT work.
> mylist=[1,2,3,4]
> mystr=str(mylist)
>
> newlist= list(mystr)
>
> I keep thinking there must be a simple way of get this done.

You can use eval() but that is generally discouraged as a security hole.

If the list will just contain integers you can do something ad hoc:
In [7]: mylist=[1,2,3,4]

In [8]: mystr=str(mylist)

In [10]: newlist = map(int, mystr[1:-1].split(','))

In [11]: newlist
Out[11]: [1, 2, 3, 4]

In Python 3 you can use ast.literal_eval().
>>> mylist = [1, 2, 3, 4]
>>> mystr = str(mylist)
>>> import ast
>>> ast.literal_eval(mystr)
[1, 2, 3, 4]

You can use these recipes:
http://code.activestate.com/recipes/511473/
http://code.activestate.com/recipes/364469/

Kent