How to Access Class Variables from Methods in Python?

Accessing Class Variables in Methods

When working with classes in Python, you may encounter instances where you need to access class variables from within methods. However, simply referencing the variable within the method may result in a NameError.

The Issue

Consider the following code snippet:

<code class="python">class Foo(object):
    bar = 1

    def bah(self):
        print(bar)</code>

When attempting to run this code, you will encounter a NameError: global name 'bar' is not defined. This is because the variable bar is a class variable, and the method bah is not able to access it directly.

The Solution

To access class variables within methods, there are two options:

• self.bar: This references the instance variable, which is specific to each instance of the class.
• Foo.bar: This references the class variable, which is shared among all instances of the class.

If you intend to modify the class variable, use Foo.bar; otherwise, use self.bar.

Example

Refactoring the code snippet using the correct approach:

<code class="python">class Foo(object):
    bar = 1

    def bah(self):
        print(self.bar)  # Access the instance variable

f = Foo()
f.bah()  # Prints 1</code>

This code will print 1, accessing the instance variable. If you wish to access the class variable, simply change self.bar to Foo.bar in the print statement.

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