10.3 Controlling Access to Attributes

• Pprevious example used attributes name and balance only to get the values of those attributes
• Also can use those attributes to modify their values

from account import Account

from decimal import Decimal

account1 = Account('John Green', Decimal('50.00'))

account1.balance

Decimal('50.00')

• Set the balance attribute to an invalid negative value, then display the balance

account1.balance = Decimal('-1000.00')

account1.balance

Decimal('-1000.00')

Encapsulation

• A class’s client code is any code that uses objects of the class
• Most object-oriented programming languages enable you to encapsulate (or hide) an object’s data from the client code
  • private data

Leading Underscore (_) Naming Convention

• Python does not have private data
• Use naming conventions to design classes that encourage correct use
• By convention, Python programmers know that any attribute name beginning with an underscore (_) is for a class’s internal use only
• Attributes whose identifiers do not begin with an underscore (_) are considered publicly accessible for use in client code

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