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Python 3 Class Slots
Python Classes/Objects
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- Python 3 Class Constructor
- Python 3 Class Variable
- Python 3 Class Slots Slot
Python has been an object-oriented language since the time it existed. Due to this, creating and using classes and objects are downright easy. This chapter helps you become an expert in using Python's object-oriented programming support. If you do not have any previous experience with object. A class is the basis of all data in Python, everything is an object in Python, and a class is how an object is defined. They are the foundation of object-oriented programming and represent real-world things you want to model in your programs. You use a class to instantiate objects, which are specific instances of. I will give some introduction to the the new Python 3.7 feature DataClasses, and compare them to using traditional class attributes and slots.
Python is an object oriented programming language.
Almost everything in Python is an object, with its properties and methods.
A Class is like an object constructor, or a 'blueprint' for creating objects.
Create a Class
To create a class, use the keyword class:
Example
Create a class named MyClass, with a property named x:
Try it Yourself »Python 3 Class Slots Free Play
Create Object
Python 3 Class Constructor
Now we can use the class named MyClass to create objects:
Example
Create an object named p1, and print the value of x:
Try it Yourself »The __init__() Function
The examples above are classes and objects in their simplest form, and are not really useful in real life applications.
To understand the meaning of classes we have to understand the built-in __init__() function.
All classes have a function called __init__(), which is always executed when the class is being initiated.
Use the __init__() function to assign values to object properties, or other operations that are necessary to do when the object is being created:
Example
Create a class named Person, use the __init__() function to assign values for name and age:
def __init__(self, name, age):
self.name = name
self.age = age
p1 = Person('John', 36)
print(p1.name)
print(p1.age)
Note: The __init__() function is called automatically every time the class is being used to create a new object.
Object Methods
Objects can also contain methods. Methods in objects are functions that belong to the object.
Let us create a method in the Person class:
Example
Insert a function that prints a greeting, and execute it on the p1 object:
Python 3 Class Variable
def __init__(self, name, age):
self.name = name
self.age = age
def myfunc(self):
print('Hello my name is ' + self.name)
p1 = Person('John', 36)
p1.myfunc()
Note: The self parameter is a reference to the current instance of the class, and is used to access variables that belong to the class.
The self Parameter
The self parameter is a reference to the current instance of the class, and is used to access variables that belongs to the class.
It does not have to be named self , you can call it whatever you like, but it has to be the first parameter of any function in the class:
Example
Use the words mysillyobject and abc instead of self:
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def __init__(mysillyobject, name, age):
mysillyobject.name = name
mysillyobject.age = age
def myfunc(abc):
print('Hello my name is ' + abc.name)
p1 = Person('John', 36)
p1.myfunc()
Modify Object Properties
You can modify properties on objects like this:
Example
Set the age of p1 to 40:
Try it Yourself »Delete Object Properties
You can delete properties on objects by using the del keyword:
Example
Delete the age property from the p1 object:
Try it Yourself »Delete Objects
You can delete objects by using the del keyword:
Example
Delete the p1 object:
Try it Yourself »The pass Statement
class definitions cannot be empty, but if you for some reason have a class definition with no content, put in the pass statement to avoid getting an error.
Example
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