suggestions, comments on an "is_subdict" test

[MRAB]

On 22/04/2011 14:55, Vlastimil Brom wrote:
> Hi all,
> I'd like to ask for comments or advice on a simple code for testing a
> "subdict", i.e. check whether all items of a given dictionary are
> present in a reference dictionary.
> Sofar I have:
>
> def is_subdict(test_dct, base_dct):
>      """Test whether all the items of test_dct are present in base_dct."""
>      unique_obj = object()
>      for key, value in test_dct.items():
>          if not base_dct.get(key, unique_obj) == value:
>              return False
>      return True
>
> I'd like to ask for possibly more idiomatic solutions, or more obvious
> ways to do this. Did I maybe missed some builtin possibility?
> I am unsure whether the check  against an unique object() or the
> negated comparison are usual.?
> (The builtin exceptions are ok, in case anything not dict-like is
> passed. A cornercase like>>>  is_subdict({}, 4)
>>>> True
> doesen't seem to be worth a special check just now.)
>
You could shorten it slightly to:

def is_subdict(test_dct, base_dct):
     """Test whether all the items of test_dct are present in base_dct."""
     unique_obj = object()
     return all(base_dct.get(key, unique_obj) == value for key, value in 
test_dct.items())