"""
Ex. 4.5 from "A primer on..."
Use a command-line argument to input
the F value, use a try-except
block to handle missing or wrong 
input argument. 
"""

import sys

try:
    F = float(sys.argv[1])
except IndexError:
    print('Det mangler et kommandolinjeargument')
    exit()
except ValueError:
    print(f'Argumentet m? v?re et rent tall, ikke {sys.argv[1]}')
    exit()

C = (F - 32) * 5.0 / 9
print(f'{F} grader F er {C:.2f} grader C')

"""
Terminal> python f2c_cml_exc.py 
Det mangler et kommandolinjeargument
Terminal> python f2c_cml_exc.py 78f
Argumentet m? v?re et rent tall, ikke 78f
Terminal> python f2c_cml_exc.py 78
78.0 grader F er 25.56 grader C
"""