A Python module can be run like a script:
python fibo.py <arguments>
In this case __name__ is set to "__main__".
With the following conditional statement the file can be used as a module or as a script:
if __name__ == "__main__":
import sys
fib(int(sys.argv[1]))
The code that parses the command line will only run if the module is executed as the “main” file:
$ python fibo.py 50
1 1 2 3 5 8 13 21 34
If the module is imported, the code is not run:
>>> import fibo
>>>