Why built in functions are defined as class?

[Larz60+]

look at it this way
abs is a class of type builtin_function_or_method, abs(14) is an instance of class abs with attribute 14

>>> type(abs)
<class 'builtin_function_or_method'>

>>>type(abs(14)) # returns type of instance of abs (which is of class int)
<class 'int'>