Welcome to this exciting tutorial where we delve into the world of Python class and static variables. We strive to ensure you walk away understanding not only how to use these variables but also when and why they can be extremely useful in your coding journeys. Our objective is to make sure you see Python class and static variables as invaluable tools in your coding toolbox.
Table of contents
What are Python Class and Static Variables?
Class and static variables are integral parts of Python programming, providing invaluable functionality within a class. They are unique in the sense that they are shared across all the instances of the class.
Why are they useful?
The power of Python class and static variables shines the most when you want to retain and share states among different instances of a class or when you need a variable to be accessible to every instance. It makes your code more efficient, keeping memory usage low.
Why should you learn about Python Class and Static Variables?
They are at the core of object-oriented programming in Python, which is widely used in data analysis, machine learning, web development, and game development. By understanding class and static variables, you’re advancing down the path of mastering Python.
Now that you understand what Python class and static variables are and why you should learn them, we’ll start our coding tutorial. We promise to make it as engaging as possible!
Python Class Variables
Let’s kick things off with Python class variables. Class variables are defined within a class but outside any of the class’s methods.
class MyClass: class_variable = "This is a class variable"
As you can see, the class variable class_variable is shared amongst all instances of the class.
class_instance1 = MyClass() class_instance2 = MyClass() print(class_instance1.class_variable) print(class_instance2.class_variable)
The output of this will be identical as the class variable retains the same value across all instances of the class.
Modifying Class Variables
We can also modify the class variable from an instance of the class, and it will be reflected in all other instances.
class_instance1.class_variable = "modified class variable" print(class_instance1.class_variable) print(class_instance2.class_variable)
Python Static Variables
Now, let’s move on to static variables. Static variables are variables that belong to a class rather than an instance of the class.
class MyClass: def my_method(): MyClass.static_variable = "This is a static variable"
Much like class variables, static variables share their values across all instances of their class.
class_instance1 = MyClass() class_instance2 = MyClass() MyClass.my_method() print(class_instance1.static_variable) print(class_instance2.static_variable)
This will produce the same output, showcasing the shared nature of static variables across class instances.
Modifying Static Variables
You can also directly modify static variables using the class name much like the way we modified the class variable earlier.
MyClass.static_variable = "modified static variable" print(class_instance1.static_variable) print(class_instance2.static_variable)
This will allow you to see that modifying static variables impacts all instances of the class since they’re all sharing the same reference to the variable.
Immutable and Mutable Class Variables
With Python class variables, it’s important to understand that immutable objects are not shared between instances, but mutable objects are. Let’s illustrate this with code examples.
class MyClass: mutable_variable =  immutable_variable = "immutable" class_instance1 = MyClass() class_instance2 = MyClass() class_instance1.mutable_variable.append(1) class_instance1.immutable_variable = "changes" print(class_instance1.mutable_variable) print(class_instance2.mutable_variable) print(class_instance1.immutable_variable) print(class_instance2.immutable_variable)
As you can see, changes to mutable class variables appear in every instance, but changes to immutable class variables do not.
Understanding Self with Class Variables
When we talk about class variables, it’s almost impossible not to mention the self keyword. Let’s see why it’s important.
class MyClass: class_variable = "original" class_instance1 = MyClass() class_instance2 = MyClass() class_instance1.class_variable = "modified" print(class_instance1.class_variable) print(class_instance2.class_variable)
In this example, we only changed the class variable for class_instance1 because we used self. The variable for class_instance2 remains unchanged.
Python Static Variables in Instance Methods
Python static variables can also be used in instance methods.
class MyClass: static_variable = "original" def modify_static(self): self.static_variable = "modified" class_instance1 = MyClass() class_instance2 = MyClass() class_instance1.modify_static() print(class_instance1.static_variable) print(class_instance2.static_variable)
This code will modify the static variable only for the particular instance (class_instance1) that called the method.
Python Class Method vs Static Method
Python has both class methods and static methods. A class method takes the class as a parameter, while a static method doesn’t. This can affect the way class and static variables are used.
class MyClass: class_variable = "original" @classmethod def modify_class_method(cls): cls.class_variable = "modified via class method" @staticmethod def modify_static_method(): MyClass.class_variable = "modified via static method" MyClass.modify_class_method() print(MyClass.class_variable) MyClass.modify_static_method() print(MyClass.class_variable)
This shows us that within a class method, Python automatically passes the class itself as the first parameter (cls), while in a static method, we have to manually refer to the class name.
Class Variables vs Instance Variables
Class variables and instance variables have different usage scenarios depending on what you need to achieve in your Python code.
Instance variables are unique to each instance, while class variables are shared across all instances.
class MyClass: class_variable = "shared" def __init__(self): self.instance_variable = "unique" class_instance1 = MyClass() class_instance2 = MyClass() class_instance1.instance_variable = "instance 1" class_instance2.instance_variable = "instance 2" print(class_instance1.instance_variable) print(class_instance2.instance_variable) print(class_instance1.class_variable) print(class_instance2.class_variable)
In conclusion, understanding class and static variables in Python is essential to write efficient and effective code, especially in larger projects. We hope this tutorial added value to your Python coding journey. Remember, continuously practice is key to mastery!
Where to go next?
Having a firm grasp on Python class and static variables is a stepping stone in your Python journey, but there is so much more to learn and master.
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