10 Python Global Variables Best Practices

Python global variables are variables that are accessible throughout the program. They are declared outside of any function or class and can be used by any part of the program. While global variables can be useful in certain situations, they can also lead to unexpected results and difficult-to-debug errors.

In this article, we will discuss 10 best practices for using global variables in Python. By following these best practices, you can ensure that your code is more reliable and easier to maintain.

1. Avoid global variables

Global variables are accessible from anywhere in the code, which can lead to unexpected behavior and bugs. It’s also difficult to keep track of where a global variable is being used, making it hard to debug or modify your code.

Instead, try using local variables whenever possible. Local variables are only accessible within the scope they were declared in, so you don’t have to worry about them affecting other parts of your code. This makes debugging much easier since you know exactly where to look for any issues. Additionally, if you need to make changes to a variable, you can do so without worrying about breaking something else.

2. Use a single module to hold all of your global variables

Using a single module to hold all of your global variables makes it easier to keep track of them. It also helps you avoid name collisions, which can occur when two different modules have the same variable names. Additionally, using a single module for global variables allows you to easily access and modify them from any other part of your code. Finally, having a single module for global variables makes it easier to debug your code since you know exactly where to look if something goes wrong.

3. Use functions instead of global variables

Functions are more secure than global variables because they can be used to limit the scope of a variable. This means that you can control who has access to the data and how it is used.

Functions also make your code easier to read, debug, and maintain. By using functions instead of global variables, you can break up complex tasks into smaller chunks which makes them easier to understand. Additionally, if you need to change something in one part of the code, you don’t have to worry about breaking other parts of the code since each function is self-contained.

4. Use classes and instances for global state

Classes and instances provide a way to store data in an organized, structured manner. This makes it easier to access the data when needed, as well as modify or update it if necessary. Additionally, classes and instances can be used to create objects that represent real-world entities, such as customers, products, etc., which can help make your code more readable and maintainable.

Using classes and instances for global state also helps keep your code DRY (Don’t Repeat Yourself). Instead of having multiple copies of the same variable scattered throughout your codebase, you can use one class instance to store all of the related information. This will reduce the amount of code you need to write and maintain, making it easier to debug and extend your application.

5. Use globals() to access global variables from within a function

The globals() function returns a dictionary of all the global variables in your program. This means that you can access any global variable from within a function without having to explicitly pass it as an argument. This makes your code more concise and easier to read, since you don’t have to keep track of which variables are global and which aren’t.

It also helps prevent accidental changes to global variables, since they won’t be modified unless you explicitly call the globals() function. Finally, using the globals() function is faster than passing each global variable as an argument, since it only requires one function call instead of multiple.

6. Use the built-in __main__ module

The __main__ module is a special Python module that allows you to define global variables and functions in the same file. This makes it easier to keep track of your code, as all of your global variables and functions are defined in one place. It also helps with debugging, since any errors related to global variables or functions will be easy to spot.

Additionally, using the __main__ module can help make your code more organized and readable. By keeping all of your global variables and functions in one place, it’s easier for other developers to understand what your code is doing.

7. Use threading locks to prevent race conditions

Race conditions occur when two or more threads try to access the same global variable at the same time. This can lead to unexpected results, as each thread may be trying to modify the value of the variable in different ways. To prevent this from happening, you should use a threading lock to ensure that only one thread is able to access the global variable at any given time. This will help keep your code safe and reliable.

8. Use only immutable objects as global constants

Immutable objects are those that cannot be changed after they have been created. This means that if you use an immutable object as a global constant, it will remain the same throughout your program’s execution and won’t be accidentally modified by any other part of your code.

Using only immutable objects as global constants also helps to ensure that all parts of your program can access the same value for the global variable, which is important for consistency. Additionally, using immutable objects makes debugging easier since you don’t need to worry about unexpected changes in the values of your global variables.

9. Use docstrings to document global variables

Docstrings are a great way to provide context and explanation for global variables. They can help other developers understand the purpose of the variable, how it should be used, and any potential pitfalls that may arise from using it. This is especially important when working with complex or unfamiliar code.

Additionally, docstrings make it easier to search for specific variables in your codebase. By including keywords related to the variable’s purpose, you can quickly find what you’re looking for without having to manually scan through lines of code.

10. Use logging for debugging

Logging allows you to track the values of global variables over time, which can be useful for debugging. It also helps you identify potential issues with your code before they become a problem.

Logging is especially helpful when dealing with complex applications that use multiple threads and processes. By logging the value of global variables at different points in the program’s execution, you can quickly pinpoint where an issue may have occurred. This makes it much easier to debug and fix any problems that arise.