import sys

try:
    F = float(sys.argv[1])
except IndexError:
    print('Please provide a command line argument')
    sys.exit(1)
except ValueError:
    print('Command line argument must be a number')
    sys.exit(1)


C = 5.0/9 * (F-32)
print('%4.2f degrees F is %4.2f degrees C' %(F,C))

"""
f2c_cml_exc.py 7.0
7.00 degrees F is -13.89 degrees C
Terminal> python f2c_cml_exc.py
Please give a command line argument
Terminal> python f2c_cml_exc.py tmp
Wrong value of command line argument
Terminal> python f2c_cml_exc.py seven
Wrong value of command line argument
Terminal> sundnes$ python f2c_cml_exc.py seven
Command line argument must be a number
"""