Is int() a standalone function or it is actually an _init_ constructor method of the int class under covers?

Question

(a) I am trying to figure out whether int(), float(), tuple() and similar functions are standalone functons or they work like constructors for user classes (i.e. invoking class __init__() method under covers.)

(b) I wanted to find available signatures of these methods, like int(str), int(str, base).

(c) I tried peeking into the source code on github, but it seems to be implemented on the c-layer, not on Python-layer. There is even no header-like stub Python code for this.

Answer 1

Yes, all of those are classes, they are class objects. Their type is type (which itself, is a class, a metaclass):

>>> type(int)
<class 'type'>

Same as a custom class:

>>> class Foo: pass
...
>>> type(Foo)
<class 'type'>

And seemingly paradoxically:

>>> type(type)
<class 'type'>

NOTE: None of these objects are the __init__. That is a special method that gets called by the constructor to run custom initialization. IOW:

>>> Foo.__init__ is Foo
False