classes, inheritance [beginner] Python

Question

Hey I'm new to this python thing. Have few days to learn all about classes but at the beginning I have problem. I got this kind of error TypeError: __init__() missing 1 required positional argument: 'nazwa'. Can you help me with solution? I want to print out calculation for my object.

class Figura(object):
 def __init__(self,nazwa):
 self.nazwa = nazwa
 def calculate(self):
 print(self.nazwa)
class Kolo(Figura):
 def __init__(self,nazwa,promien):
 Figura.__init__(self)
 self.promien = promien
 def calculate(self):
 Figura.calculate(self)
 print(2 * 3.1415 * promien)
kolo1 = Kolo('kolo',4)
kolo1.calculate()

Answer 1

You'll need to pass on the nazwa argument in the Kolo.__init__() method call:

class Kolo(Figura):
 def __init__(self, nazwa, promien):
 Figura.__init__(self, nazwa)
 self.promien = promien

You may want to use the super() function there instead and avoid having to repeat the parent class:

class Kolo(Figura):
 def __init__(self, nazwa, promien):
 super().__init__(nazwa)
 self.promien = promien
 def calculate(self):
 super().calculate()
 print(2 * 3.1415 * self.promien)

Note that I corrected your Kolo.calculate() method as well; you want to refer to self.promien rather than make promien a local name.

Demo:

>>> class Figura(object):
... def __init__(self,nazwa):
... self.nazwa = nazwa
... def calculate(self):
... print(self.nazwa)
...
>>> class Kolo(Figura):
... def __init__(self, nazwa, promien):
... super().__init__(nazwa)
... self.promien = promien
... def calculate(self):
... super().calculate()
... print(2 * 3.1415 * self.promien)
...
>>> kolo1 = Kolo('kolo',4)
>>> kolo1.calculate()
kolo
25.132