{"id":1292,"date":"2020-04-14T04:40:36","date_gmt":"2020-04-14T11:40:36","guid":{"rendered":"https:\/\/renanmf.com\/?p=1292"},"modified":"2021-06-10T11:59:24","modified_gmt":"2021-06-10T14:59:24","slug":"if-__name__-__main__-python","status":"publish","type":"post","link":"https:\/\/renanmf.com\/if-__name__-__main__-python\/","title":{"rendered":"if __name__ == ‘__main__’ in Python"},"content":{"rendered":"

You are on the process of building a module with the basic math operations add<\/code>, subtract<\/code>, multiply<\/code>, divide<\/code> called basic_operations<\/code> saved in the basic_operations.py<\/code> file.<\/p>\n

To guarantee everything is fine, you make some tests.<\/p>\n

def add(a, b):\n    return a + b\n\ndef subtract(a, b):\n    return a - b\n\ndef multiply(a, b):\n    return a * b\n\ndef divide(a, b):\n    return a \/ b\n\nprint(add(10, 2)) \nprint(subtract(10,2))\nprint(multiply(10,2))\nprint(divide(10,2))<\/code><\/pre>\n
After running the code:<\/p>\n
python3 basic_operations.py<\/code><\/pre>\n
The output is:<\/p>\n
12\n8\n20\n5.0<\/code><\/pre>\n
The output for those tests are what we expected.<\/p>\n
Our code is right and ready to share.<\/p>\n
Let’s import the new module run it in the Python console.<\/p>\n
Python 3.6.9 (default, Nov  7 2019, 10:44:02) \n[GCC 8.3.0] on linux\nType "help", "copyright", "credits" or "license" for more information.\n>>> import basic_operations\n12\n8\n20\n5.0\n>>> <\/code><\/pre>\n
When the module is imported our tests are displayed on the screen even though we didn’t do anything besides importing basic_operations<\/code>.<\/p>\n
To fix that we use if __name__ == '__main__'<\/code> in the basic_operations.py<\/code> file like this:<\/p>\n
def add(a, b):\n    return a + b\n\ndef subtract(a, b):\n    return a - b\n\ndef multiply(a, b):\n    return a * b\n\ndef divide(a, b):\n    return a \/ b\n\nif __name__ == '__main__':\n    print(add(10, 2)) \n    print(subtract(10,2))\n    print(multiply(10,2))\n    print(divide(10,2))<\/code><\/pre>\n
Running the code directly on the terminal will continue to display the tests, but when you import it like a module, the tests won’t show and you can use the functions the way you intended.<\/p>\n
Python 3.6.9 (default, Nov  7 2019, 10:44:02) \n[GCC 8.3.0] on linux\nType "help", "copyright", "credits" or "license" for more information.\n>>> import basic_operations\n>>> basic_operations.multiply(10,2)\n20\n>>><\/code><\/pre>\n
Now that you know how to use the if __name__ == '__main__'<\/code>, let’s understand how it works.<\/p>\n
The condition tells when the interpreter is treating the code as a module or as a program itself being executed directly.<\/p>\n
Python has this native variable called __name__<\/code>.<\/p>\n
This variable represents the name of the module which is the name of the .py<\/code> file.<\/p>\n
Create a file my_program.py<\/code> with the following and execute it.<\/p>\n
print(__name__)<\/code><\/pre>\n
The output will be:<\/p>\n
__main__<\/code><\/pre>\n
This tells us that when a program is executed directly, the variable __name__<\/code> is defined as __main__<\/code>.<\/p>\n
But when it is imported as a module, the value of __name__<\/code> is the name of the module.<\/p>\n
Python 3.6.9 (default, Nov  7 2019, 10:44:02) \n[GCC 8.3.0] on linux\nType "help", "copyright", "credits" or "license" for more information.\n>>> import my_program\nmy_program\n>>><\/code><\/pre>\n
This is how the Python interpreter differentiates the behavior of an imported module and a program executed directly on the terminal.<\/p>\n","protected":false},"excerpt":{"rendered":"
You are on the process of building a module with the basic math operations add, subtract, multiply, divide called basic_operations saved in the basic_operations.py file. To guarantee everything is fine, you make some tests. def add(a, b): return a + b def subtract(a, b): return a – b def multiply(a, b): return a * b […]<\/p>\n","protected":false},"author":3,"featured_media":742,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[6],"class_list":["post-1292","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-python","tag-python"],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":6}},"yoast_head":"\nif __name__ == '__main__' in Python<\/title>\n<meta name=\"description\" content=\"Uderstand the use of if __name__ == '__main__' in Python\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/renanmf.com\/if-__name__-__main__-python\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"if __name__ == '__main__' in Python\" \/>\n<meta property=\"og:description\" content=\"Uderstand the use of if __name__ == '__main__' in Python\" \/>\n<meta property=\"og:url\" content=\"https:\/\/renanmf.com\/if-__name__-__main__-python\/\" \/>\n<meta property=\"og:site_name\" content=\"Renan Moura - 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