Parsing command-line options

Set default values of the script's input parameters:

m = 1.0; b = 0.7; c = 5.0; func = 'y'; A = 5.0; 
w = 2*math.pi; y0 = 0.2; tstop = 30.0; dt = 0.05; 
case = 'tmp1'; screenplot = 1

Examine command-line options in sys.argv:

# read variables from the command line, one by one:
while len(sys.argv) >= 2:
    option = sys.argv[1];       del sys.argv[1]
    if   option == '-m':
        m = float(sys.argv[1]); del sys.argv[1]
    elif option == '-b':
        b = float(sys.argv[1]); del sys.argv[1]
    ...

Note: sys.argv[1] is text, but we may want a float for numerical operations