Summary

The provided web content explains the purpose and significance of the if __name__ == '__main__': statement in Python scripts, which determines whether a script is being run directly or imported as a module and controls the execution of code accordingly.

Abstract

The article "Python’s if name==‘main’ Statement Explained" delves into the usage and benefits of the if __name__ == '__main__': construct in Python. It clarifies the role of the __name__ variable, which holds the value '__main__' when a script is executed directly and the module name when it is imported. The author emphasizes that enclosing code within this if statement ensures that it only runs when the script is the main program, preventing unintended side effects when the module is imported elsewhere. This feature is particularly useful for creating reusable modules and maintaining clean code practices, allowing developers to avoid executing certain operations when a module is being imported for its functions or classes. The article also provides practical examples to illustrate how checking the __name__ variable can help manage code execution in multiple script environments.

Opinions

The author suggests that the if __name__ == '__main__': statement is essential for Python scripts intended to be reused as modules in other scripts.
The article implies that understanding the __name__ variable is crucial for writing modular and maintainable Python code.
It is conveyed that the use of this statement is a best practice in Python, especially in object-oriented programming projects that involve multiple scripts and modules.
The author expresses that beginners might find the if __name__ == '__main__': statement confusing at first, but its importance becomes clear as one progresses in Python programming.
The article promotes the idea that using the if __name__ == '__main__': statement is a sign of good coding practice and is beneficial for the organization and structure of Python projects.

Python’s if name==‘main’ Statement Explained

Uncover what this statement does and why you should use it in your own scripts

Photo by Kevin Ku: https://www.pexels.com/photo/data-codes-through-eyeglasses-577585/

Starting out with Python, you’ve likely written code in the following format:

def function():
     pass

function()

In other words, your operations typically entail creating a function or class and then calling it. Simple, right?

If this applies to you, you might be a bit confused when you see other scripts that follow the format:

def function():
     pass

if __name__ == '__main__':
     function()

It’s a very similar approach, where a function/class is called after it is created, but this time, the call is performed within the code block of the an if statement that you’ve probably seen numerous times:

if __name__ == '__main__'

If begs the question: what does this if statement do? Why is it so commonly used in Python scripts? Why don’t people just run their functions and classes without running this check?

When I first attempted to answer these questions by reading on the web, I ended up more confused than when I initially began my search.

To save anyone else the trouble, I attempt to explain (in simple terms) why this statement is so popular in Python and why you should incorporate it into your own scripts.

The name Variable

First, let’s discuss Python’s special variable: __name__. The value of the __name__ variable depends on how the script it is used in is executed. It stores the string “__main__” if the script is being executed directly and stores the name of the module of interest when the file is being imported.

Ok, that was a mouthful.

For the sake of clarity, we can demonstrate this special variable with two Python scripts: ‘file1.py’ and ‘file2.py’.

In the script called ‘file1.py’, let’s print the value of the __name__ variable.

The value of __name__ is “__main__”, which means that the file the variable is used in is being executed directly.

Now, in file2.py, let’s import ‘file1' and then print the __name__ variable for the file1 module.

This time, the __name__ variable is equal to ‘file1’, which is the name of the imported module.

Checking The name Variable

Now that we know what the __name__ variable signifies, it’s easy to see the purpose of the if statement:

if __name__ == '__main__'

The statement checks if the script is being executed directly or if it is imported. Any operations within the code block of the if statement will only be executed if the file of interest is being run directly.

Application

So what use cases are there for such a feature?

In short, checking the value of the __name__ variable with this if statement enables users to avoid running certain operations when importing a module. This makes it easier to reuse components from one module (e.g., classes and functions) in other scripts.

Example

Once again, the importance of checking the __name__ variable is easier to demonstrate with an example.

In file1.py, let’s create a function called get_len, which returns the number of characters in a given text. After that, we can use it to print the length of the text ‘Hello World!’.

Cool, we are able to use the function to find the number of characters in any given string. However, at some point, we might wish to incorporate this function into a different script for a separate use case.

Let’s use the get_len function in the script in ‘file2.py’ by importing the file1 module. This time, we wish to find the number of characters in the text “Goodbye World!”.

Hmmm… The output shows us the number of characters in “Goodbye World!”, but it also shows the result of the function call for the string “Hello World!” we performed in file1. This is not what we asked for.

A simple way to avoid executing the unwanted function call in file1.py would be to modify the file by adding the if __name__=='__main__' statement before the function call so that the function is only used when the file is run directly (i.e., it won’t be called if the file is imported).

Let’s try running file2.py again (we don’t need to make any changes to this file).

Fantastic! We are now able to use the imported get_len function in file2.py without executing the function call in file1.py!

Conclusion

Ultimately, those using Python as a procedural programming tool in projects that only require a single script (e.g., data analysis) don’t really need to worry about using the if __name__ == '__main__' statement.

However, Python is an object-oriented programming (OOP) language and promotes operations that are facilitated by the interaction of objects. Checking the __name__ variable with the if statement will be useful for applications that require reusing code by importing classes or functions from other files without executing any unwanted operations.

Happy coding!

Python’s if __name__==‘__main__’ Statement Explained