How to make data attributes private in python

Question

I'm new to Python, and I need some help understanding private methods. I'm working on an assignment where I have to output the type of pet it is, its name, and age. I have the program working but I seem to be stuck on how I would go about making the data attributes private. This is my code.

import random       
class pet :
#how the pets attributes will be displayed
def __init__(animal, type, name, age): 
    animal.type = type            
    animal.name = name
    animal.age = age
    #empty list for adding tricks
    animal.tricks = []
#number of fleas are random from 0 to 10
fleaCount = random.randint(0,10)    
def addTrick(animal, trick):
    animal.tricks.append(trick)       
def petAge(animal):
    return animal.age         
def printInfo(animal):        
    print(f"Pet type : {animal.type} \nPet name : {animal.name}\nPet age : {animal.age}\nPet                            fleas : {animal.fleaCount}")
    print("Tricks :")      
    for i in range(len(animal.tricks)):
        print("",animal.tricks[i])

# main program


#dog1 information
dog1 = pet("Dog","Max",10)        
dog1.addTrick("Stay and Bark")              
dog1.printInfo()                
#dog2 information
dog2 = pet("Dog","Lily",8)
dog2.addTrick("Play Dead and Fetch")
dog2.printInfo()
#cat1 information
cat1 = pet("Cat","Mittens",11)
cat1.addTrick("Sit and High Five")
cat1.printInfo()

Python doesn't generally use private attributes, but you can see this stackoverflow post on how to create `@property` flags: https://stackoverflow.com/questions/4555932/public-or-private-attribute-in-python-what-is-the-best-way — Mason Caiby, Sep 25 '19 at 19:50
Why do you think you need to make the attributes private? The assignment doesn't seem to require it. — Daniel Roseman, Sep 25 '19 at 21:18
@DanielRoseman The teacher wants us to make the attributes private for the assignment. — user1761498, Sep 25 '19 at 21:24

score 1 · Accepted Answer · answered Sep 25 '19 at 19:51

Private properties in an object is defined by prepending it with __, so in your case it would be __age instead of age. The interpreter will then mangle the name (i.e. it would not be accessible directly through __age), but if someone wanted to get access through the mangled name, they could still do it. There is no such thing as a real private property in Python.

Also: the first parameter to an objects method in python should always be named self (and not animal).

When I add __ before my objects the programs runs blank. Why is that happening? — user1761498, Sep 25 '19 at 21:45

score 1 · Answer 2 · answered Sep 25 '19 at 20:01

1

Just use double underscore before the attribute name, for example: "__type", "__age", "__name".

If you want to learn more about public, private and protected: https://www.tutorialsteacher.com/python/private-and-protected-access-modifiers-in-python

answered Sep 25 '19 at 20:01

Luis Quiroga

718
2
7
22

How to make data attributes private in python

2 Answers2