Re: Keys in dict and keys not in dict

[Andrew Z]

Beautiful.
Thank you Chris, Ben, Peter and Inada.

On Mar 19, 2018 3:14 AM, "INADA Naoki"  wrote:

> > expected = {"foo", "bar", "spam"}
> > missing = expected - set(json.keys())
> >
>
> dict.keys() returns set-like object.
> So `missing = expected - json.keys()` works fine, and it's more efficient.
>
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Re: Keys in dict and keys not in dict

[INADA Naoki]

> expected = {"foo", "bar", "spam"}
> missing = expected - set(json.keys())
>

dict.keys() returns set-like object.
So `missing = expected - json.keys()` works fine, and it's more efficient.

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Re: Keys in dict and keys not in dict

[Peter Otten]

Ben Finney wrote:

> Chris Angelico <ros...@gmail.com> writes:
> 
>> Sounds like a set operation to me.
>>
>> expected = {"foo", "bar", "spam"}
>> missing = expected - set(json)
> 
> That works (because iterating a dict returns its keys). But it is less
> immediately understandable, IMO, than this::
> 
> expected = {"foo", "bar", "spam"}
> missing = expected - set(json.keys())

There's no need to materialize the set of keys: 

>>> expected = {"foo", "bar", "ham"}
>>> json = dict(foo=1, bar=2, spam=3)
>>> expected - json.keys()
{'ham'}

In Python 2 use json.viewkeys() instead of keys().

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Re: Keys in dict and keys not in dict

[Chris Angelico]

On Mon, Mar 19, 2018 at 3:18 PM, Ben Finney <ben+pyt...@benfinney.id.au> wrote:
> Chris Angelico <ros...@gmail.com> writes:
>
>> Sounds like a set operation to me.
>>
>> expected = {"foo", "bar", "spam"}
>> missing = expected - set(json)
>
> That works (because iterating a dict returns its keys). But it is less
> immediately understandable, IMO, than this::
>
> expected = {"foo", "bar", "spam"}
> missing = expected - set(json.keys())
>

Sure, whichever way you want to do it. Either way, it's a set
difference operation that gives the OP's desired information.

ChrisA
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Re: Keys in dict and keys not in dict

[Ben Finney]

Chris Angelico <ros...@gmail.com> writes:

> Sounds like a set operation to me.
>
> expected = {"foo", "bar", "spam"}
> missing = expected - set(json)

That works (because iterating a dict returns its keys). But it is less
immediately understandable, IMO, than this::

expected = {"foo", "bar", "spam"}
missing = expected - set(json.keys())

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 \ “The greater the artist, the greater the doubt; perfect |
  `\   confidence is granted to the less talented as a consolation |
_o__)   prize.” —Robert Hughes |
Ben Finney

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Re: Keys in dict and keys not in dict

[Chris Angelico]

On Mon, Mar 19, 2018 at 2:32 PM, Andrew Z  wrote:
> hello,
>
>  i'd like to check if a function parameter (json) has all the keys I expect
> it to have and if it doesn't - point out the one that is missing.
>
>  What's the good way of doing that?
>
> "good way" - something concise... i'd like to avoid using :
>  if key in json:
> #pass
>  else
>print(" Oops, i did it again ...")

Sounds like a set operation to me.

expected = {"foo", "bar", "spam"}
missing = expected - set(json)
if missing:
print("Missing keys:", missing)

ChrisA
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Keys in dict and keys not in dict

[Andrew Z]

hello,

 i'd like to check if a function parameter (json) has all the keys I expect
it to have and if it doesn't - point out the one that is missing.

 What's the good way of doing that?

"good way" - something concise... i'd like to avoid using :
 if key in json:
#pass
 else
   print(" Oops, i did it again ...")

thank you
AZ
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