How to understand python classes?

Question

Hello I'm learning python, it is also my first language. I'm trying to figure out how classes work. I have this small code and I can't get it to work after a week of searching. Thank you for helping me.

Also I'm trying to figure out what getattr and super do. I read on the documentation but its not easy for me to understand. English is not my native language and its a little difficult to understand sometimes.If you can explain this two things or if you know any website that explains it in a simple way I would really thank you for it.

here is the code:

import sys


class Map(object):
    dicti = {'stuff': stuff(),
             'more_stuff': more_stuff()
    }

    class Stuff:

        def stuff(self):
            print "did it work?"
            next = raw_input("type next: ")

            if next == "next":
                return 'more_stuff'
            else:
                print "what? lets try again."
                return 'stuff'      

    class MoreStuff:

        def more_stuff(self):
            print "ok"

            next = raw_input('type next: ')

            if next == "next":
                return 'stuff'

            else:
                print "bye."
                sys.exit(0)


class NewClass(Map):

    def __init__(self, themap):

        self.themap = themap

    def Continu(self):

        next = self.themap

        while True:
            print "----"

            room = next()




a_test = NewClass('stuff')
a_test.Continu()

Answer 1

The problem with your class is that it doesn't seem to represent anything (sorry if that's harsh). Rather than fix your code, I'll just show you a couple examples.

These are example classes that I wrote. The first one is kind of ridiculous, but actually simple and could teach you something. It uses hasattr which is not a far stretch from getattr.

You're classes can have logic in them, but try to see them as ways of managing information about an object. I mean object in both the python sense and in the normal meaning of the word.

Also, I noticed you have some other classes indented under Map. Just work with classes as separate things for now. Indenting those like that does not give them any special relationship to Map

class OppMan:

    def __init__(self, awake = False):

        self.truth = awake
        self.answers = 0


    def echo(self, userIn):

        if type(userIn) == (int or float):
            answer = -1*self.truth*userIn

        elif hasattr(userIn, '__str__') or hasattr(userIn, '__repr__'):
            answer = 'not '*self.truth + str(userIn)

        else:
            try:
                answer = -1*userIn
            except:
                answer = 'I am only human'

        self.answers += 1
        return answer

Example usage:

Barney = OppMan(True)

print(Barney.echo(420))
print(Barney.echo('yours'))
print(Barney.echo(['a','b','c']))
print(Barney.answers)


Betty = OppMan()

print(Betty.echo('you figure it out'))

This one is like fractions, sort of:

class Rational:

    def __init__(self, numer, denom):
        self.n = numer
        self.d = denom



    def __add__(self, other):
        return Rational((self.n*other.d)+(self.d*other.n), self.d*other.d)

    def __mul__(self, other):
        return Rational(self.n*other.n, self.d*other.d)

    def __str__(self):
        return str(self.n) + '/' + str(self.d)

Example usage:

foo = Rational(3,5)
bar = Rational(1,7)
print(foo+bar)


foo = Rational('3','5')
bar = Rational(1,2)
print(foo+bar)

I'm not sure what you're trying to do with the "room", dictionary, etc., but study these and try to find some simple problems to solve. It might take a while to figure out how these work, but you'll know more about classes in the end.

Answer 2

You are passing the string 'stuff' into NewClass, so that is becoming self.themap

later you are assigning next = self.themap, so now next is also a reference to the string 'stuff'.

room = next() will fail because you can't call a string