«

once again, probably a trivial question but i googled and didn't
get an obvious solution. how to list the attributes of a *class*?

eg., i was playing with dicts and noticed that the type returned by
the keys() method was "dict_keys". so i'm now curious as to the
attributes of the dict_keys class. but i don't know how to look at
that without first *creating* such an instance, then asking for
"dir(dk)".

surely there's a simpler way just using the class name, no?

rday

p.s. any recommendations for the most concise reference sheet for
python 3 that exists? being able to print off the entire language
spec on two or four pages and tacking it up in front of me would be
just ducky. thanks.

--

================================================== ======================
Robert P. J. Day Waterloo, Ontario, CANADA

Linux Consulting, Training and Kernel Pedantry.

Web page: http://crashcourse.ca
Twitter: http://twitter.com/rpjday
================================================== ======================

* Robert P. J. Day:
> once again, probably a trivial question but i googled and didn't
> get an obvious solution. how to list the attributes of a *class*?
>
> eg., i was playing with dicts and noticed that the type returned by
> the keys() method was "dict_keys". so i'm now curious as to the
> attributes of the dict_keys class. but i don't know how to look at
> that without first *creating* such an instance, then asking for
> "dir(dk)".

Like,

dir( list )

where 'list' is the built-in type.

There's a pretty-printer for that somewhere, but I can't recall.

And as I also recommended in your thread "examining an initial, pristine python3
shell session",

help( list )

or more generally

help( "list" )


> surely there's a simpler way just using the class name, no?

Yes.


> rday
>
> p.s. any recommendations for the most concise reference sheet for
> python 3 that exists? being able to print off the entire language
> spec on two or four pages and tacking it up in front of me would be
> just ducky. thanks.

Sorry, don't know.


Cheers & hth.,

- Alf

On Sun, 24 Jan 2010, Alf P. Steinbach wrote:

> * Robert P. J. Day:
> > once again, probably a trivial question but i googled and didn't
> > get an obvious solution. how to list the attributes of a *class*?
> >
> > eg., i was playing with dicts and noticed that the type returned by
> > the keys() method was "dict_keys". so i'm now curious as to the
> > attributes of the dict_keys class. but i don't know how to look at
> > that without first *creating* such an instance, then asking for
> > "dir(dk)".
>
> Like,
>
> dir( list )
>
> where 'list' is the built-in type.
>
> There's a pretty-printer for that somewhere, but I can't recall.

except that doesn't work for

>>> dir(dict_keys)

so what's the difference there?

rday
--

================================================== ======================
Robert P. J. Day Waterloo, Ontario, CANADA

Linux Consulting, Training and Kernel Pedantry.

Web page: http://crashcourse.ca
Twitter: http://twitter.com/rpjday
================================================== ======================

* Robert P. J. Day:
> On Sun, 24 Jan 2010, Alf P. Steinbach wrote:
>
>> * Robert P. J. Day:
>>> once again, probably a trivial question but i googled and didn't
>>> get an obvious solution. how to list the attributes of a *class*?
>>>
>>> eg., i was playing with dicts and noticed that the type returned by
>>> the keys() method was "dict_keys". so i'm now curious as to the
>>> attributes of the dict_keys class. but i don't know how to look at
>>> that without first *creating* such an instance, then asking for
>>> "dir(dk)".
>> Like,
>>
>> dir( list )
>>
>> where 'list' is the built-in type.
>>
>> There's a pretty-printer for that somewhere, but I can't recall.
>
> except that doesn't work for
>
> >>> dir(dict_keys)
>
> so what's the difference there?

'list' is a built-in type that by default is available.

'dict_keys' is a type that you're not meant to use directly, so it's not made
available by default.

The 'type' function yields the type of its argument, so you *can* do e.g.

DictKeys = type( {}.keys() )

dir( DictKeys )
list( vars( DictKeys ) )
help( DictKeys )

It doesn't help much though because the only method of interrest is __iter__,
which produces an iterator that you can use e.g. in a for loop or to construct a
list, whatever.

The relevant place to find out more about keys() is in the documentation.


Cheers & hth.,

- Alf

24-01-2010, 17:37:41 Alf P. Steinbach <> wrote:

> DictKeys = type( {}.keys() )
>
> dir( DictKeys )
> list( vars( DictKeys ) )
> help( DictKeys )
>
> It doesn't help much though because the only method of interrest is
> __iter__

Not only. Please, consider:

>>> dictkeys = type({}.keys())
>>> set(dir(dictkeys)).difference(dir(object))
{'__ror__', '__rsub__', '__and__', '__rand__', '__contains__',
'__len__', '__iter__', '__or__', '__rxor__', '__xor__', '__sub__'}

And e.g. comparision-related mehods (__gt__, __le__ and so on) also are
more interensing in dict keys views than in plain object() instances...

Regards,

*j