newbie question - can't make code work

[deanhystad]

The message is pretty clear. Python expects you to indent like this:

class Animal:
 
    class Mammal(Animal):
 
m = Mammal ()
print (isinstance(m, Mammal))
print (isinstance(m, Animal))

But now you get this eror:

Error:
    m = Mammal ()
IndentationError: expected an indented block after class definition on line 3

So the problem is not indenting so much as python expects the code following the class declaration to be indented.

You could follow the class declaration by an actual class definition.

class Animal:
    def some_method(self, value):
        self.a = value
 
class Mammal(Animal):
    def some_other_method(self, value):
        self.b = value
 
m = Mammal ()
print (isinstance(m, Mammal))
print (isinstance(m, Animal))

Or you could use a placeholder.

class Animal:
    pass
 
class Mammal(Animal):
    pass
 
m = Mammal ()
print (isinstance(m, Mammal))
print (isinstance(m, Animal))

Or a docstring.

class Animal:
    """Kingdom of living things that are not plants."""
 
class Mammal(Animal):
    """An animal that produces milk."""
 
m = Mammal ()
print (isinstance(m, Mammal))
print (isinstance(m, Animal))