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suggestions, comments on an "is_subdict" test

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  suggestions, comments on an "is_subdict" test Vlastimil Brom <vlastimil.brom@gmail.com> - 2011-04-22 15:55 +0200
    Re: suggestions, comments on an "is_subdict" test Irmen de Jong <irmen.NOSPAM@xs4all.nl> - 2011-04-22 16:57 +0200
      Re: suggestions, comments on an "is_subdict" test MRAB <python@mrabarnett.plus.com> - 2011-04-22 16:18 +0100
        Re: suggestions, comments on an "is_subdict" test Raymond Hettinger <python@rcn.com> - 2011-04-23 00:23 -0700
      Re: suggestions, comments on an "is_subdict" test Paul Rubin <no.email@nospam.invalid> - 2011-04-23 00:26 -0700

#3869 — suggestions, comments on an "is_subdict" test

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.)

Thanks in advance for the suggestions,
  regards,
      vbr

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#3879

On 22-4-2011 15:55, 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 would use:

test_dct.items() <= base_dct.items()

-irmen

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#3881

On 22/04/2011 15:57, Irmen de Jong wrote:
> On 22-4-2011 15:55, 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 would use:
>
> test_dct.items()<= base_dct.items()
>
In Python 2:

 >>> test_dct = {"foo": 0, "bar": 1}
 >>> base_dct = {"foo": 0, "bar": 1, "baz": 2}
 >>>
 >>> test_dct.items() <= base_dct.items()
False

In Python 3:

 >>> test_dct = {"foo": 0, "bar": 1}
 >>> base_dct = {"foo": 0, "bar": 1, "baz": 2}
 >>> test_dct.items() <= base_dct.items()
True

YMMV

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#3905

On Apr 22, 8:18 am, MRAB <pyt...@mrabarnett.plus.com> wrote:
> On 22/04/2011 15:57, Irmen de Jong wrote:
>
>
>
>
>
>
>
> > On 22-4-2011 15:55, 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 would use:
>
> > test_dct.items()<= base_dct.items()
>
> In Python 2:
>
>  >>> test_dct = {"foo": 0, "bar": 1}
>  >>> base_dct = {"foo": 0, "bar": 1, "baz": 2}
>  >>>
>  >>> test_dct.items() <= base_dct.items()
> False
>
> In Python 3:
>
>  >>> test_dct = {"foo": 0, "bar": 1}
>  >>> base_dct = {"foo": 0, "bar": 1, "baz": 2}
>  >>> test_dct.items() <= base_dct.items()
> True
>
> YMMV

That is because it is spelled differently in Python 2.7:

>>> test_dct = {"foo": 0, "bar": 1}
>>> base_dct = {"foo": 0, "bar": 1, "baz": 2}
>>> test_dct.viewitems() <= base_dct.viewitems()
True

Raymond

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#3906

Irmen de Jong <irmen.NOSPAM@xs4all.nl> writes:
> I would use:
> test_dct.items() <= base_dct.items()

I think you need an explicit cast:

  set(test_dct.items()) <= set(base_dct.items())

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