Getters And Setters

Getters

Getters return the value of a property. They may also make a small modification of the returned result.

Let's look the following example:

class Square: __side = 5 # default value for __side prop def get_side(self): return self.__side sqObj = Square() print(sqObj.get_side())

Output:

5

Members that have __ prefix are meant to be accessed only inside the class body.

If we need to access it outside the class body a getter needs to be defined.

Basically get_side accesses the private member __side.

Accessing a private member (__side in this case) won't throw exception but it's a good coding convention private members to be accessed only inside the class body.

Setters

Setters allow for a property to be modified. They are important since they can provide validation before a value is set.

Together getters and setters can control access and modification of a class member.

Let's look at the following example:

class Person: def get_age(self): return self.__age def set_age(self, value): if value < 0: value = 0 self.__age = value obj1 = Person() obj1.set_age(20) print(obj1.get_age()) obj2 = Person() obj2.set_age(-10) print(obj2.get_age())

Output:

20 0

Explanation:

• __age is a private member (because it has __ prefix) so it's supposed to be accessed / modified via it's getters and setters.
• For obj1 a value of 20 is set for the __age property via it's setter - set_age.
• For obj2 a value of -10 is attempted to be set for the __age property. Due to the validation at line 6 a value of 0 is set.

Why using getters and setters?

Because private members can have validation before modification (setter) and controlled access (getter).

It seems easier to have only public members (without __ prefix). This way there is no need for getters and setters. It's a better practice to have private members that are accessed with getter and modified through setter. This way a validation can be provided in a setter and the public access can be done only to some members - those which have getters.