python - Why does this class run?

Question

I've been playing with my codes a little for a while, and this one is not about a bug or anything, but i just don't understand why class main() runs without needing to initialize it...

class vars():
    var1 = "Universe!"
    var2 = "Oscar!"
    var3 = "Rainbow!"

class main():
    print (vars.var1)
    def __init__(self):
        print (vars.var2)
        print (vars.var3)

But yes, thank you very much for reading.

Answer 1

Unlike many other languages, class body is an executable statement in Python and is executed immediately as the interpreter reaches the class line. When you run this "program":

class Foo:
    print("hey")

it just prints "hey" without any Foo object being created.

The same applies to the function definition statement def (but not to function bodies). When you run this:

def foo(arg=print("hi")):
    print("not yet")

it prints "hi", but not "not yet".