If this file is being imported from another module, __name__ will be set to the modules name.__name__ is a built-in variable which evaluates to the name of the current module. Next, you use print() to print a sentence describing the purpose of this code. On line 21, main() is defined. them and how they interact with each other. Natural Language Processing (NLP) Tutorial. How to Check a Number is Palindrome in Python? It essentially serves as a starting point for the execution of a program. Note: The following examples are defined using syntax 1, try to convert them in syntax 2 for practice. The third print() will first print the phrase The value of __name__ is, and then it will print the representation of the __name__ variable using Pythons built-in repr(). With our online interpreter, you can test and debug your code in real-time, all from your web browser. The following example uses arguments and parameters that you will learn later in this article so you can come back to it again if not understood. Adding the -m argument runs the code in the __main__.py module of a package. block. Python exec () Function Example x = 8 exec('print (x==8)') exec('print (x+4)') Output: True 12 Python sum () Function import systems reference for details on how this works. How to Call a Function in Python Guide | Python Central This is better than putting the code directly into the conditional block because a user can reuse main() if they import your module. What is the Format Function in Python and How does it work? Example A variable created outside of a function is global and can be used by anyone: x = 300 def myfunc (): print(x) myfunc () print(x) Try it Yourself (Of course, this would be anti-social. And as I said before, the value of this string depends on how the code is being executed. Complete . By using our site, you Types of Functions in Python with Examples | Edureka The import process caused the Python interpreter to execute all of the lines of code in the best_practices.py file, so the output shows the line explaining the purpose of the file. Both of these mechanisms are related to Python modules; how users interact with attribute as its interactive. I, personally, like these semantics. My code is terminated without output when I remove the if. User-defined function: We can create our own functions based on our requirements. How to create a virtual ISO file from /dev/sr0. By importing the necessary code from one Python file to another. That way, any other programmers who read your script immediately know that this function is the starting point of the code that accomplishes the primary task of the script. My course does not explain the main method in python. How to Create a Basic Project using MVT in Django ? Look at the following piece of code: In the above example, I have used the definition of main(), which contains the program logic I want to run. Python Database Connection: Know how to connect with database. directly from the command line using the -m flag. As seen above, when File1.py is run directly, the interpreter sets the __name__ variable as __main__ and when it is run through File2.py by importing, the __name__ variable is set as the name of the python script, i.e. Thus, it can be said that if __name__ == __main__ is the part of the program that runs when the script is run from the command line using a command like Python File1.py. If you did not use if the script would be run at times where you don't want it to such as importing that module. If used, an if __name__ == '__main__' block will still work as expected A Computer Science portal for geeks. Vote for difficulty. Manually raising (throwing) an exception in Python. Your task is to find the minimum and maximum elements in the array. What is Python language? Upcoming Batches For Python Certification Training Course, To understand more about python main function, lets have, Got a question for us? Data Structures You Need To Learn In Python, Python Programming Beginners Guide To Python Programming Language. The if statement allows you to create a main function which will be executed if your file is loaded as the "Main" module rather than as a library in another module. Practice | GeeksforGeeks | A computer science portal for geeks In the above example, I have defined a function called getgot() to fetch the data. Ive also defined a function called demo, to include a piece of code, that can be reused as and when necessary. For better code reusability, better understanding and for overall code optimization. What are Generators in Python and How to use them? Uncommenting the The Python interpreter will execute the from time import sleep and print() lines that are outside the function definition, then it will create the definition of the function called process_data(). Install Python On Windows Python 3.X Installation Guide. module is present in sys.modules, Python passes that to namely. Convert Infix expression to Postfix expression - GeeksforGeeks / Infix What is Python Spyder IDE and How to use it? Python and Netflix: What Happens When You Stream a Film? The team members who worked on this tutorial are: Master Real-World Python Skills With Unlimited Access to RealPython. Note: For more information on how importing works in Python, check out Python import: Advanced Techniques and Tips as well as Absolute vs Relative Imports in Python. __name__ variable supports to verify if the file of python is being run . In this example, we will create a simple function to check whether the number passed as an argument to the function is even or odd. However, Python interpreter runs the code right from the first line. Now when we import a Python script as module the __name__ variable gets the value same as the name of the python script imported. When you execute a script, you will not be able to interactively define the code that the Python interpreter is executing. This data is passed to process_data(), which returns the modified_data. Python supports various types of arguments that can be passed at the time of the function call. During this process, the python interpreter sets the __name__ value to the module name if the Python source file is imported as a module. The way that you tell the computer to execute code from the command line is slightly different depending on your operating system. for a __main__.py file within a package, because its __name__ # for demonstration purposes, you can imagine that there is some, # valuable and reusable logic inside this function, """Echo the input arguments to standard output""", # next section explains the use of sys.exit. Once the Python interpreter imports the file, you can use any variables, classes, or functions defined in the module youve imported. If you put a print statement before the if __name__ line then it will print output every time any other code attempts to import that as a module. Apply Filter This function is often called the entry point because it is where execution enters the program. Python Packaging User Guide attribute will include the packages path if imported: This wont work for __main__.py files in the root directory of a .zip file It provides with a huge amount of Classes and function which help in analyzing and manipulating data in an easier way. To help understand how this code will execute, you should first understand how the Python interpreter sets __name__ depending on how the code is being executed. The first string after the function is called the Document string or Docstring in short. Inside the conditional block, you have added four lines of code (lines 12, 13, 14, and 15): Now, run your best_practices.py script from the command line to see how the output will change: First, the output shows the result of the print() call outside of process_data(). As a result, you end up writing the conditional if statement as follows: Hence, if the conditional statement evaluates to True, it means, the .py (Python Script) file is being run or executed directly. The __name__ identifier is bound to the name of any module as it's being imported. The contents of __main__.py typically isnt fenced with Python dictionary is a built-in type that supports key-value pairs. Now you should check what happens when you import the best_practices.py file from the interactive interpreter (or another module).