[Tutor] How to get the keys of a dict inside a dict. ValueError: too many values to unpack

[Steve Willoughby]

On 07-Aug-11 08:37, Kayode Odeyemi wrote:
> Hello all,
>
> Please I need help figuring out this permutation.
>
> I have a dict like this:
>
> x = "{'pk': 1L, 'model': 'trans', 'fields': {'updated': 2011, 'tel':
> 3456}", "{'pk': 2L, 'model': 'trans2', 'fields': {'updated': 2011,
> 'tel': 34510}";

First of all, that's not a dict.  It's just a tuple of strings.
so, when you say:

> #loop through and get the keys of each
> for k,v in x:

You'll get one iteration, where k=the first string and v=the second.
However, you ignore k and v in all the code that follows, so I'm really 
confused what you're trying to do here.

>      keys = dict(x).keys()

Now you try to create a dict out of a tuple of strings, which won't 
quite work as written but in principle would only have created a 
dictionary with the first string as the key, and the second as value, 
not nested dictionaries.

The dict() constructor really expects to see a sequence of key/value 
pairs, so it's going to take your sequence x as a list of two such 
pairs, and then raise an exception because the strings are not key/value 
pairs.  This would succeed if you said
   keys = dict((x,)).keys()
perhaps, but it's still not at all what you're trying to accomplish.

> print keys

Note that you are re-assigning the value of keys each time through the 
loop but printing its last value after the loop exits.  Is that what you 
intended?


You're expecting Python to take a string that looks like Python source 
code and know that you want it to be interpreted as source code. 
Instead of using string values, use actual Python syntax directly, like:

  x = {
	'pk': 1L,
	'model': 'trans',
	'fields': {
		'updated': 2011,
		'tel': 3456
	}
}


-- 
Steve Willoughby / steve at alchemy.com
"A ship in harbor is safe, but that is not what ships are built for."
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