if __name__ == '__main__':

     with open('test.py') as f:

         exec(f.read())

 import os

 from subprocess import call

 if __name__ == '__main__':

     os.system('ls')

     call('ls', shell=True)

 from subprocess import getoutput

 if __name__ == '__main__':

     output = getoutput('dir')

     print(output)

 import os

 if __name__ == '__main__':

     output = os.popen('dir').readlines()

     for out in output:

         print(out, end='')

 from subprocess import Popen, PIPE

 if __name__ == '__main__':

     f = Popen('dir', shell=True, stdout=PIPE).stdout

     for line in f:

         print(line, end='')

 import sys

 def my_exit_func():

     print('show message')

 sys.exitfunc = my_exit_func

 def usage():

     print('At least 2 args required')

     print('Usage: test.py arg1 arg2')

     sys.exit(1)

 argc = len(sys.argv)

 if argc < 3:

     usage()

 print('number of args entered:', argc)

 print('args were:', sys.argv)

 import os

 while True:

     cmd = input('#: ')

     if cmd == 'exit':

         break

     else:

         output = os.popen(cmd).readlines()

         for out in output:

             print(out, end='')

 x = 3

 def foo(x):

     if x > 0:

         return True

     return False

 foo.tester = '''

 if foo(x):

     print('PASSED')

 else:

     print('FAILED')

 '''

 if hasattr(foo, 'tester'):

     print('Function "foo(x)" has a tester... executing')

     exec(foo.tester)

 else:

     print('Function "foo(x)" has no tester... skipping')