CODEWITHSUNDEEP
pythonfunctionclassnamespaces
enrico.bacis
enrico.bacis

Reputation: 31504

List all the elements in a python namespace

Python classes contain namespaces and the function dir lists the content of the namespace.

The object namespace contains several functions, for example the function __subclasses__ that, when invoked, returns a list containing all the known classes that are subclasses of object.

The output of dir(object) is:

['__class__', '__delattr__', '__doc__', '__format__', '__getattribute__',
 '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__',
 '__setattr__', '__sizeof__', '__str__', '__subclasshook__']

The __subclasses__ function is not listed, but it's there, try: object.__subclasses__().

I understand that a class can change the __dir__ dictionary to customize what dir shows, but that's not the case of object, in fact object.__dir__ raises an exception.

Still, when I use IPython autocompletion, the __subclasses__ function is there. How can I obtain the same list of elements that IPython uses so that I know that also __subclasses__ is there?

Upvotes: 2

Views: 16308

Answers (1)

user2357112
user2357112

Reputation: 280887

IPython finds __subclasses__ through perfectly ordinary means, by looking at type(object). On the other hand, since object is a type, dir for types specifically does not look at type(object). Whoever wrote dir decided seeing metaclass attributes in the list would be confusing.

Upvotes: 5

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