dict order

[Robert Bossy]

Peter Otten wrote:
> Robert Bossy wrote:
>
>   
>> I wish to know how two dict objects are compared. By browsing the
>> archives I gathered that the number of items are first compared, but if
>> the two dict objects have the same number of items, then the comparison
>> algorithm was not mentioned.
>>     
>
> If I interpret the comments in 
>
> http://svn.python.org/view/python/trunk/Objects/dictobject.c?rev=64048&view=markup
>
> correctly it's roughly
>
> def characterize(d, e):
>     return min(((k, v) for k, v in d.iteritems() if k not in e or e[k] != v),
>                key=lambda (k, v): k)
>
> def dict_compare(d, e):
>     result = cmp(len(d), len(e))
>     if result:
>         return result
>     try:
>         ka, va = characterize(d, e)
>     except ValueError:
>         return 0
>     kb, vb = characterize(e, d)
>     return cmp(ka, kb) or cmp(va, vb)
Thanks, Peter! That was exactly what I was looking for. Quite clever, I 
might add.

RB