Python 2.7 Ineritance get parent method properties

Question

I am a newbie and have confused learning OOP on python. I am trying to inherit class also using super, but it didn't work as expected.

here my code.

parent.py

class Sale(http.Controller):

    def cart(self, **post):
        order = request.website.sale_get_order()
        ....
        return request.render("website_sale.cart", values)

child.py

import Sale as sale

class SaleExtend(sale):

    def cart(self, **post):
        if order:
        # do something
    ....

    return super(SaleExtend, self).cart(**post)

I got an error,

AttributeError: 'Sale (extended by SaleExtend)' object has no attribute 'order'

if I just use pass its work correctly, but how to get order value from a parent?

or I did it wrong.

indentation errors, `self.order` ... simply `order` inside a funciton is function scope and gone if you leave the function. Read about [scopes](https://stackoverflow.com/questions/291978/short-description-of-the-scoping-rules) — Patrick Artner, Apr 15 '19 at 15:42
You haven't defined an instance variable `order` anywhere, merely a local variable — juanpa.arrivillaga, Apr 15 '19 at 16:16
@DickyRaambo no, **you never define an instance variable `order` anywhere**. Where do you think that is happening? — juanpa.arrivillaga, Apr 15 '19 at 23:12

score 0 · Accepted Answer · answered Apr 16 '19 at 06:18

You have no instance nor a class variable order:

class Sale(http.Controller):

    def cart(self, **post):
        # FUNCTION SCOPE - exists only inside the function
        order = request.website.sale_get_order()  
        ....
        return request.render("website_sale.cart", values)

Class variables are created like so:

class Ale():
    content = "Lager"     # this is shared between all instances -> "static"

Instance variables are created like so:

class Ale():
    def __init__(self, ale_type):
        self.content = ale_type       # this is different for each instance unless you 
                                      # create multiple instances with the same ale_type
                                      # but they are still "independent" of each other

Function scope variables are creates like so:

class Ale():

    # ....

    def doSomething(self):
        lenContent = len(self.content)      # function scope
        print( self.content, lenContent )

    def doElse(self):
        print(lenContent)   # NameError - does not exist in scope

See Resolution of names and Short description of the scoping rules?

Python 2.7 Ineritance get parent method properties

1 Answers1