[Tutor] Inserting one dictionary into another

[Kent Johnson]

On Thu, Jan 1, 2009 at 11:04 AM, Keith Reed <keith_reed at fastmail.net> wrote:
> I'm having trouble assigning a dictionary as a value within another:
>
>
> -------- Code Snippet Start --------
>
>        for line in fromchild.readlines():
>                itemarray = line.strip().split(":")
>                parentdictkey = itemarray[0]
>                print 'parentdictkey = ' + parentdictkey
>                for index in range(len(headerinfo)):
>                        nesteddict[headerinfo[index]] = itemarray[index]
>                #print nesteddict
>                parentdict[parentdictkey] = nesteddict
>                nesteddict.clear()
>        print
>        '-------------------------------------------------------------------------\n'
>        print parentdict

The problem is that you are re-using the same dict rather than
creating a new one each time through the loop. Every value of
parentdict is the same; when you clear nesteddict you are clearing the
one shared dict.

Python assignment copies references, not values. If you don't
understand this, read this:
http://personalpages.tds.net/~kent37/kk/00012.html

The solution is easy; just make a new dict at the start of the loop:
  nesteddict = {}
and get rid of the clear().

Kent