"""
 special.py

 looking at one of python's special 
 variables, __name__ ... and showing a doctest (in double())

 There are two ways to run this, which do different things :

  1. Running python itself from the command prompt.
       $ python special.py
       __name__ is __main__

  2. After an "import", within an interactive python session
       $ python
       >>> from special import *
       >>> main()
       __name__ is special

"""

def double(x):
    """ return twice x 
        >>> double(10)
        20
    """
    return 2*x

def main():
    print(" __name__ is ", __name__)
    print(" double(3) is ", double(3))

def is_it_between(x):
    # another way to do things similar to "else"
    if x > 10:
        print("x is bigger than 10")
        return
    if x < 3:
        print("x is smaller 3")
        return
    
if __name__ == '__main__':
    import doctest
    doctest.testmod()
    main()