Python - 为什么类列在内置函数列表中？

Question

The Python docs lists property() as a built-in function .

However, the function description has the keyword "class" in front of it in the docs.

class property (fget=None, fset=None, fdel=None, doc=None)

This also happens with

class set ([iterable])

and

class slice (stop)

What does this mean? - why are classes listed under built-in functions. Is this just a documentation issue or is there a technical reason?

EDIT: I am not asking about how property() works.

Answer 1

The Python glossary defines a function as:

A series of statements which returns some value to a caller. It can also be passed zero or more arguments which may be used in the execution of the body.

A class can be passed arguments, and returns a value to the caller, so arguably by this definition classes are functions*.

In addition (as deceze points out in the comments), a class should always return an instance of itself – set , property , slice , etc. all return instances of set , property , slice , etc. respectively – so set , property and friends are all also classes, and so they are documented as such:

class set ([ iterable ])

meaning that set is a class, not that it returns one.

I would guess that set etc. are documented in the "built-in functions" page because a) they are callable, and b) it's convenient to have all the documentation for "things you can call" in one place.

*Strictly speaking, isinstance(C, types.FunctionType) is false for any class C (as far as I can tell), but classes are certainly callables ( isinstance(C, typing.Callable) is true), which is maybe a more useful property to think about.