Global Variables in Python

In Python, a global variable is a variable that is defined outside of a function or a class. This means that it can be accessed and modified from any part of the program. Global variables are useful when you need to store data that needs to be shared across multiple functions or classes. In this article, we will explore the concept of global variables in Python and how to use them in your code.

How to Define Global Variables in Python

To define a global variable in Python, you simply declare the variable outside of any function or class. Here’s an example:

global_var = 10

def my_func():
    print(global_var)

my_func() # Output: 10

In this example, we have defined a global variable named global_var outside of the function my_func(). Inside the function, we directly use the variable name without the need for the global keyword to access the global variable.

How to Modify Global Variables in Python

Modifying the value of a global variable inside a function or class requires the global keyword followed by the variable name. Here’s an example:

global_var = 10

def my_func():
    global global_var
    global_var = 20

my_func()
print(global_var) # Output: 20

In this example, we have defined a global variable named global_var and a function named my_func(). Inside the function, we use the global keyword followed by the variable name to indicate that we want to modify the global variable, not create a new local variable with the same name. We then assign a new value of 20 to the global variable.

How to Access Global Variables in Python

Accessing the value of a global variable from within a function or a class does not require the global keyword. Here’s an example:

global_var = 10

def my_func():
    print(global_var)

my_func() # Output: 10

In this example, we have defined a global variable named global_var and a function named my_func(). Inside the function, we directly use the variable name to print the value of the global variable.

Using Global Variables in Classes

Global variables can also be used inside classes. Here’s an example:

global_var = 10

class MyClass:
    def my_method(self):
        print(global_var)

obj = MyClass()
obj.my_method() # Output: 10

In this example, we have defined a global variable named global_var and a class named MyClass. Inside the class, we have defined a method named my_method() that simply prints the value of the global variable.

Avoiding Global Variables in Python

While global variables can be useful in some cases, they should generally be avoided as much as possible. This is because global variables can make your code harder to understand, maintain, and debug. Instead, you should try to use local variables and pass data between functions and classes using arguments and return values.

Conclusion

In this article, we have explored the concept of global variables in Python and how to use them in your code. We have seen how to define global variables, modify their values, and access them from within functions and classes. We have also discussed the importance of avoiding global variables and using local variables instead. With this knowledge, you should now be able to use global variables effectively in your Python programs (but remember to use them sparingly).