[issue27544] Document the ABCs for instance/subclass checks of dict view types

[Irit Katriel]

Change by Irit Katriel :


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versions: +Python 3.11 -Python 3.5, Python 3.6

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[issue27544] Document the ABCs for instance/subclass checks of dict view types

[Emanuel Barry]

Changes by Emanuel Barry :


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title: documentiona of dict view types -> Document the ABCs for 
instance/subclass checks of dict view types

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[issue27544] Document the ABCs for instance/subclass checks of dict view types

[Terry J. Reedy]

Terry J. Reedy added the comment:

The view objects *are* built-ins, but are not exposed in the __builtins__ 
module.  This is true of many internal types, perhaps even a majority. The 
function and list_iterator classes are other examples.

>>> type(lambda: 0)

>>> type(iter([]))


A few such 'hidden' classes are exposed in the types module.

"This module provides names for many of the types that are required to 
implement a Python interpreter. It deliberately avoids including some of the 
types that arise only incidentally during processing such as the listiterator 
type.

Typical use of these names is for isinstance() or issubclass() checks."

The function class is.

"types.FunctionType
types.LambdaType

The type of user-defined functions and functions created by lambda 
expressions."
  
The list_iterator class is not. Perhaps the rationale is that there is no 
reason to know whether an iterator is iterating over a list, tuple, range, set, 
frozenset, dict, or anything else.  They are all used the same.  On the other 
hand, Different view types are used a bit differently.

Types includes a generic MappingProxyType.  Perhaps you should propose adding 
the specific dict view types.  Or you can create them yourself.
  KeysViewType = type({}.keys())
  ValuesViewType = type({}.values())
  ItemsViewType = type({}.items())
This is the code that would be used in the module if they were added there.

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nosy: +terry.reedy
versions:  -Python 3.2, Python 3.3, Python 3.4

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[issue27544] Document the ABCs for instance/subclass checks of dict view types

[Jeffrey McLarty]

Change by Jeffrey McLarty :


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nosy: +Jeffrey McLarty

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