The statement 'if __name__ == '__main__'' is used to determine if a Python script is being run directly or imported as a module. It allows you to execute code conditionally, ensuring that certain parts only run when the script is the main program.

In Python, the statement if __name__ == '__main__': serves a crucial purpose in distinguishing between running a script directly and importing it as a module in another script. When a Python file is executed, Python assigns the name __main__ to the module being run. However, when the same file is imported into another script, its name is set to the file name. This distinction allows developers to create modules that can both provide reusable functionality and execute specific code when run as standalone scripts. By encapsulating code within this conditional statement, you ensure that certain parts of the script—such as test cases, example usage, or initialization code—are only executed when the script is the entry point. For instance, if you have a module that defines various functions and classes, you can include tests within the if __name__ == '__main__': block to verify functionality without executing these tests when the module is imported elsewhere. This practice not only enhances code reusability but also improves the modularity of your codebase. Overall, understanding the significance of if __name__ == '__main__': is essential for any Python developer, as it contributes to writing clean, maintainable, and reusable code.