Python program start

Question

Should I start a Python program with:

if__name__ == '__main__': some code... 

And if so, why? I saw it many times but don't have a clue about it.

Answer 1

If your program is usable as a library but you also have a main program (e.g. to test the library), that construct lets others import the file as a library and not run your main program. If your program is named foo.py and you do "import foo" from another python file, __name__ evaluates to 'foo', but if you run "python foo.py" from the command line, __name__ evaluates to '__main__'.

Note that you do need to insert a space between if and _, and indent the main program:

if __name__ == '__main__':     main program here 

Answer 2

A better pattern is this:

def main():    ...  if __name__ == '__main__':    main() 

This allows your code to be invoked by someone who imported it, while also making programs such as pychecker and pylint work.