append to list - instance attribute

Question

I want to add a list as a Python class instance attribute (i.e. not a class attribute), and then add a class method which will append items to the list.

e.g. we have an Employee class and each employee may have won different awards which will be stored in a list.

class Employee:
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary
        employeeAwards = []

    def addAward(self, Award):
        employeeAwards.append(Award)

However if do this, I get an "unresolved reference" error on the instance attribute (employeeAwards).

Where should I declare the class instance attribute?

You want a class method that appends to an instance attribute?! Or do you mean an instance method? — jonrsharpe
– jonrsharpe, Commented Jul 15, 2015 at 12:09
self.employeeAwards = [] and then self.employeeAwards.append(Award) — Tometzky
– Tometzky, Commented Jul 15, 2015 at 12:09

tamasgal · Accepted Answer · 2015-07-15 12:08:48Z

3

You need to bind it to self:

class Employee:
    def __init__(self, name, salary):
        self.name = name
        self.salary = salary
        self.employeeAwards = []

    def addAward(self, Award):
        self.employeeAwards.append(Award)

answered Jul 15, 2015 at 12:08

tamasgal

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Comments

Community · Accepted Answer · 2017-05-23 11:51:12Z

1

I think septi pointed out the correct solution already: bind it to self.

Here's an interesting discussion about class vs instance variables: Every variable (or method) you bind to self is in fact an instance variable.

Class variables would look like this:

class Employee(object):
    employeeAwards = []

    def __init__(self, name, salary):
        ...

edited May 23, 2017 at 11:51

CommunityBot

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answered Jul 15, 2015 at 12:13

adrianus

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1 Comment

Avizipi Over a year ago

This is also a valid answer, but you should be careful when using a list as a class attribute. Pay attention that when using append to the list, you are actually updating the class attribute and not the instance attribute.

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