What makes [a, b, c ... ] a list?

Question

To create/get an object/instance of a user-defined class we do:

<obj_name> = <class>([<some_object>])

And the same is true for built-in classes:

E.g., a = int(), a = int(2.7) etc.

But what makes a mere integer also an int object?
In general, how do these become an instance of respective classes?

5 int
3.2 float
[8, 1] list
etc.

And to my knowledge only built-in classes support this way to create objects.

Answer 1

The system knows about its kernel built-in s.
The best fitting is chosen.

but it cant guess user classes.
if u want this behaviour, you could try to work with factory classes.

Answer 2

In python we have type() function to get type of input we have given

Answer 3

ａｂｈｉｎａｖ Yup, the interpreter knows that 12 is an object of the int class. This is a built-in behaviour. So 12 isn't actually an int but a reference to an int object containing the value '12' (I guess that class properties make this possible). You can check this out with the following code:

print(id(12))
a = 12
print(id(a))

Answer 4

Thanks Oma Falk
I believe it's related to the (conversions made by) interpreter.
But what are factory classes?

Answer 5

You're right Sâgærāvürï but what I'm asking is completely different