PYTHON MAIN FUNCTION

PYTHON MAIN FUNCTION is a starting point of any program. When the program is run, the python interpreter runs the code sequentially. Main function is executed only when it is run as a Python program. It will not run the main function if it imported as a module.

def main():
     print ("hello world!")
print ("Python")

Here, we got two pieces of print- one is defined within the main function that is "Hello World" and the other is independent, which is "Python". When you run the function def main ():

• Only "Python" prints out
• and not the code "Hello World."

It is because we did not declare the call function "if__name__== "__main__". It is important that after defining the main function, you call the code by if__name__== "__main__" and then run the code, only then you will get the output "hello world!" in the programming console. Consider the following code

def main():
    print("hello world!")  
if __name__ == "__main__":
    main()
print("Python")

• When Python interpreter reads a source file, it will execute all the code found in it.
• When Python runs the "source file" as the main program, it sets the special variable (__name__) to have a value ("__main__").
• When you execute the main function, it will then read the "if" statement and checks whether __name__ does equal to __main__.
• In Python "if__name__== "__main__" allows you to run the Python files either as reusable modules or standalone programs.

The __name__ variable and Python Module

def main():
    print("hello world!")
if __name__ == "__main__":
    main()
print("Python ")
print("Value in built variable name is:  ",__name__)