Classes, Subclass and None Error message.

Question

Hi, so I wrote the following code...

class Animal:
def noise(self):
print("noise")
class Dog(Animal):
def noise(self):
print("woof")
class Hog(Animal):
def noise(self):
print("snort")
print(Animal().noise(), "xx ", Dog().noise(),"xx ", Hog().noise())

And the output I get is:

noise
woof
snort
None xx None xx None

Then when I delete the line of code with the print method, ie

class Animal:
def noise(self):
print("noise")
class Dog(Animal):
def noise(self):
print("woof")
class Hog(Animal):
def noise(self):
print("snort")
#print(Animal().noise(), "xx ", Dog().noise(),"xx ", Hog().noise())

Then the output is..
.. there's not output.

I do not understand what's going on here
In the first code version, I expected the output would be "noise xx bark xx snort".

A) Why was the output
noise
bark
snort
on separate lines and without the xx?
B)
Why did None xx None xx None print?
C)
Why when in the second version and I got rid of the print function, was there no output? I expected it to be
noise
bark
snort
on separate lines

Thanks!

Answer 1

Hi Ariella,

A)
Because of the call to print in the methods.

B)
None is automatically returned by a function that doesn't have any other return value. Your methods only print something but don't return anything.

C)
Because you didn't call the methods.

Hope that helps.