Object oriented python constructor and class methods

Question

#!/usr/bin/env python

class SportsCar(object):

        def __init__(self,make,colour):
                self.make = make
                self.colour = colour
                self.horn = "BEEEEEEEEPPPPPPP"

        def honk(self):
                #now we can make some noise!
                print self.make,'  ',self.colour,'  ',self.horn
                print "Done "


mycar = SportsCar('Honda','silver')
#print mycar.make 
#print mycar.colour

print mycar.honk()


print "Good Bye!!"

The output of the above code is given below.

Honda    silver    BEEEEEEEEPPPPPPP
Done 
None
Good Bye!!

The first two lines of the output

Honda    silver    BEEEEEEEEPPPPPPP
Done

This is printed by mycar.honk().

I also understand the 4th line

Good Bye!!

I don't understand from where 'None' in the third line come from? Can someone please explain?

Also another related question

what is the difference between the declerations

class SportsCar:

and

class SportsCar(object):

I have been seeing both the declerations in different places.?

One question per question, please. – Henry Keiter Apr 02 '13 at 20:56 — Henry Keiter, Apr 02 '13 at 20:56

score 9 · Accepted Answer · answered Apr 02 '13 at 20:29

9

Functions always have a return value, None by default.

You are printing the return value of the .honk() method, which is the default None:

print mycar.honk()

You can just call mycar.honk() without the print statement. The method does it's own printing.

answered Apr 02 '13 at 20:29

Martijn Pieters

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See http://stackoverflow.com/questions/54867/old-style-and-new-style-classes-in-python – Martijn Pieters Apr 02 '13 at 21:01

score 0 · Answer 2 · answered Apr 02 '13 at 20:32

0

You're not returning anything in your honk method, therefore it returns None by default.

answered Apr 02 '13 at 20:32

Kyle Getrost

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Object oriented python constructor and class methods

2 Answers2