Now when we import a Python script as module the __name__ variable gets the value same as the name of the python script imported. And on execution, it prints Hello, World!. This is No matter which way of running your code youre using, Python defines a special variable called __name__ that contains a string whose value depends on how the code is being used. an import statement: For a more detailed look at how __name__ is set in all situations, see GeeksforGeeks. This is my file to demonstrate best practices. Can you tell me which line is executed first in my code ? Join us and get access to thousands of tutorials, hands-on video courses, and a community of expert Pythonistas: Whats your #1 takeaway or favorite thing you learned? Whether to apply this practice to your code is a judgment call on your part. 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. Next, you use print() to print a sentence describing the purpose of this code. Python Functions is a block of statements that return the specific task. Python program with main() method does not run, The last else clause in python does not work. The echo.py example from Thats an ", "The variable __name__ tells me which context this file is running in.". The following example illustrates Default arguments. earlier exemplifies using the sys.exit(main()) convention. What Isinstance In Python And How To Implement It? Python is a great language for performing data analysis tasks. The second function definition on line 12 creates and returns some sample data, and the third function definition on line 17 simulates writing the modified data to a database. Python - Move all files from subfolders to main folder, Python - Copy Files From Subfolders to the Main folder. There is also a conditional (or if) statement that checks the value of __name__ and compares it to the string "__main__". A-143, 9th Floor, Sovereign Corporate Tower, We use cookies to ensure you have the best browsing experience on our website. The main () is considered a unique function for several programming languages, also referred to as the point of execution for a program file. Specifically, the outputs of the calls to print() that are inside the definition of process_data() are not printed! FIFA World Cup 2018 Best XI: Analyzing Fifa Dataset Using Python, Scikit learn Machine Learning using Python, The Why And How Of Exploratory Data Analysis In Python, OpenCV Python Tutorial: Computer Vision With OpenCV In Python, Tkinter Tutorial For Beginners | GUI Programming Using Tkinter In Python, Introduction To Game Building With Python's Turtle Module, PyGame Tutorial Game Development Using PyGame In Python, PyTorch Tutorial Implementing Deep Neural Networks Using PyTorch. As a developer generalist, Bryan does Python from the web to data science and everywhere inbetween. 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(). By proactively following this convention ourselves, our module will have the Arguments are the values passed inside the parenthesis of the function. How to Implement a Linked List in Python? Hence, having a defined starting point for the execution of your Python program is useful to better understand how your program works. As we already know the def keyword is used to define the normal functions and the lambda keyword is used to create anonymous functions. Uncommenting the Technical detail: The Python documentation defines specifically when __name__ will have the value '__main__': A modules __name__ is set equal to '__main__' when read from standard input, a script, or from an interactive prompt. Next, your script called process_data() and passed data in for modification. A Computer Science portal for geeks. It encourages programmers to separate functionality (definitions) from function (execution) and encourages re-use. For example, print () - prints the string inside the quotation marks sqrt () - returns the square root of a number pow () - returns the power of a number These library functions are defined inside the module. This example uses repr() to emphasize that the value of __name__ is a string. This data is passed to process_data(), which returns the modified_data. For example: sys.exit(main()) By the end of this article, youll understand: Free Download: Get a sample chapter from Python Tricks: The Book that shows you Pythons best practices with simple examples you can apply instantly to write more beautiful + Pythonic code. Any code that is not protected by that guard will be executed upon execution or importing of the module. Regardless of your operating system, the output from the Python scripts that you use in this article will be the same, so only the Linux and macOS style of input is shown in this article, and the input line will start at the $. Python with Tkinter outputs the fastest and easiest way to create GUI applications. Unsubscribe any time. Complete . A variable created in the main body of the Python code is a global variable and belongs to the global scope. Python Seaborn Tutorial: What is Seaborn and How to Use it? Those other modules can then be What is Random Number Generator in Python and how to use it? Given a sorted array of size N and an integer K, find the position(0-based indexing) at which K is present in the array using binary search. Top 4 Advanced Project Ideas to Enhance Your AI Skills, Top 10 Machine Learning Project Ideas That You Can Implement, 5 Machine Learning Project Ideas for Beginners in 2022, 7 Cool Python Project Ideas for Intermediate Developers, Essential Python Tips And Tricks For Programmers, Python Input Methods for Competitive Programming, Vulnerability in input() function Python 2.x, Important differences between Python 2.x and Python 3.x with examples, Statement, Indentation and Comment in Python, How to assign values to variables in Python and other languages, Adding new column to existing DataFrame in Pandas, How to get column names in Pandas dataframe. For more details, see Intra-package References in the When you are developing a module or script, you will most likely want to take advantage of modules that someone else has already built, which you can do with the import keyword. We can create a Python function using the def keyword. Lets understand how this code executes. Apply the event Trigger on the widgets. One important thing to note is, in Python every variable name is a reference. Important Python Data Types You Need to Know, PyCharm Tutorial: Writing Python Code In PyCharm (IDE), Python Visual Studio- Learn How To Make Your First Python Program. but instead put it directly within the if __name__ == '__main__' block, The use of docstring in functions is optional but it is considered a good practice. There are two special symbols: Example 1: Variable length non-keywords argument, Example 2: Variable length keyword arguments. The semantics are a bit subtle. On Windows, the command prompt typically looks like the example below: The part before the > may look different, depending on your username. Apply function to every row in a Pandas DataFrame - GeeksforGeeks However, there are slight differences in meaning that emphasize the purpose of a piece of code: File: Typically, a Python file is any file that contains code. We have already seen some methods until now, and you may not notice them. How To Convert Lists To Strings In Python? Python Main Function is the beginning of any Python program. 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. Ethical standards in asking a professor for reviewing a finished manuscript and publishing it together. However, before doing that, it will define a few special variables. Example 1: Input: N = 5 . A 101 Guide On The Least Squares Regression Method, Python Career Opportunities: Your Career Guide To Python Programming, Top Python developer Skills you need to know, Learn How To Make A Resume For A Python Developer. The popular method for file executes as a python script. Django ModelForm Create form from Models, Django CRUD (Create, Retrieve, Update, Delete) Function Based Views, Class Based Generic Views Django (Create, Retrieve, Update, Delete), Django ORM Inserting, Updating & Deleting Data, Django Basic App Model Makemigrations and Migrate, Connect MySQL database using MySQL-Connector Python, Installing MongoDB on Windows with Python, Create a database in MongoDB using Python, MongoDB python | Delete Data and Drop Collection. Connecting Talent with Opportunities Since 2020: 2500+ Companies | 10,000+ Jobs Offered | 20 LPA Avg Salary Hire with Us Join our Hiring Contest to unlock your potential and get hired by the best! If the source file is executed as the main program, the interpreter sets the __name__ variable to have a value __main__. To understand more about python main function, lets have a look at the topics that I will be covering in this article: A function is a block of reusable code that forms the foundation of performing actions in a programming language. User-defined Exceptions in Python with Examples, Regular Expression in Python with Examples | Set 1, Regular Expressions in Python Set 2 (Search, Match and Find All), Python Regex: re.search() VS re.findall(), Counters in Python | Set 1 (Initialization and Updation), Metaprogramming with Metaclasses in Python, Multithreading in Python | Set 2 (Synchronization), Multiprocessing in Python | Set 1 (Introduction), Multiprocessing in Python | Set 2 (Communication between processes), Socket Programming with Multi-threading in Python, Basic Slicing and Advanced Indexing in NumPy Python, Random sampling in numpy | randint() function, Random sampling in numpy | random_sample() function, Random sampling in numpy | ranf() function, Random sampling in numpy | random_integers() function. On Linux and macOS, the command line typically looks like the example below: The part before the dollar sign ($) may look different, depending on your username and your computers name. More on main() - http://ibiblio.org/g2swap/byteofpython/read/module-name.html. See venv for an example of a package with a minimal __main__.py Python String Concatenation : Everything You Need To Know, Everything You Need To Know About Print Exception In Python, Top 10 Python Libraries You Must Know In 2023, Python NumPy Tutorial Introduction To NumPy With Examples, Python Pandas Tutorial : Learn Pandas for Data Analysis, Python Matplotlib Tutorial Data Visualizations In Python With Matplotlib. How to Learn Python 3 from Scratch A Beginners Guide. students: Note that from .student import search_students is an example of a relative defined in the REPL becomes part of the __main__ scope: Note that in this case the __main__ scope doesnt contain a __file__ The below syntax can be used to print out the docstring of a function: Example: Adding Docstring to the function. In most programming languages, there is a special function which is executed automatically every time the program is run. the global variable instead of a local name. Find minimum and maximum element in an array - GeeksforGeeks Python supports various types of arguments that can be passed at the time of the function call. This is where using the if __name__ == '__main__' code block comes in import. There are mainly two types of functions in Python. In this way, you can control the execution of the code, rather than letting the Python interpreter execute it as soon as it imports the module. main functions are often used to create command-line tools by specifying them as entry points for console scripts. The details of how you can execute Python from your command line are not that important for the purpose of this article, but you can expand the box below to read more about the differences between the command line on Windows, Linux, and macOS. 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(). Please mention it in the comments section of Main Function In Python blog and we will get back to you at the earliest or join, Join Edureka Meetup community for 100+ Free Webinars each month. Related Tutorial Categories: When echo.py is imported, the What is Try Except in Python and how it works? You may look at the output below: When you write full-fledged Python programs, there could be numerous functions that could be called and used. This is because the __name__ variable had the value "best_practices", so Python did not execute the code inside the block, including process_data(), because the conditional statement evaluated to False. This is followed by a conditional if statement that checks the value of __name__, and compares it to the string __main__. Defining the main function in Python In our first example, I've demonstrated the key principle of how we can separate executable code so that it runs only when executed in the top-level environment. handy. In Python, standard library functions are the built-in functions that can be used directly in our program. By importing the necessary code from one Python file to another. Top 50 Django Interview Questions and Answers You Need to Know in 2023.