type() is not a function?

Question

Python `type` is an object of class `type`. Same with int, str, map etc.

https://code.sololearn.com/cCKy3vfBMzvI/

Answer 1

Ore... I had similar questions about this a while back and was disappointed by the lack of clarification in the official documentation. I decided to review the C and Python source code directly and made the following assessment.

IIRC, these built-in functions are special functions that map directly to C functions. Therefore, technically, these are the most fundamental functions for which all other functions and classes in Python are built on. For this reason, built-in C functions, like str(), int(), type(), etc, build objects as if they're class constructors and will resolve as <class 'type'>.

While these built-in C functions might seem more like Python class constructors, perhaps it's the other way around. That is, I speculate the interface for creating objects in Python is modeled after these built-in C functions.

Makes you wonder... 😉

Also, you might be interested in my version of your code, which I created some time ago on my local computer:

https://code.sololearn.com/c26xp4s2z6zk/

Answer 2

Why does the documentation refer to them as functions when they are, in fact, constructors?

I see it was explained clearly down the page but the title "built-in functions" is misleading.

https://docs.python.org/3/library/functions.html

Answer 3

Slick If you look closely, you will notice that some of the built-ins where prefixed with 'class' e.g
'''
class bool([x])
'''

These are constructors and have a type of <class "type">

Somewhere down the page you will find this
'''
class list([iterable])

Rather than being a function, list is actually a mutable sequence type, as documented in Lists and Sequence Types — list, tuple, range.
'''

Conclusion - not all the built ins are functions. Which explains our previous findings. I just wish the documentation made this more obvious from the start.

Answer 4

I think type is the class of classes.

Answer 5

Ore Yes. isinstance(str, type) ---> True

Answer 6

David Carroll Thanks for the answer. I will check the code when I have time.

Answer 7

makes sense since python is so uppity about EVERYTHING is a class (or part of one) funny find though.

Answer 8

Slick I think you meant that everything is an object. Yes. That is true but functions are also object. So `type` would still be an object if it was a function.

Answer 9

https://code.sololearn.com/cyJ8e7zJ0hNW/?ref=app

Answer 10

I just checked as well that is a bit weird. Then i tried type checking "all" and it comes out as what's expected (function or built in method)! I think it may be how each is made induvidually

Answer 11

Seb TheS I don't understand. Are you saying every class is an instance of `type`? 😲

Answer 12

Seb TheS It's all too confusing for me 🧐

Answer 13

type is like the base object. Similar to Object in JavaScript or stdClass in PHP?!

I am trying to compare this with what I already know.