For parsing command-line input argument in a script Python has the old argparse, optparse, and getopt modules. A new development is the docopt module that I have been using a bit for scripts related to Responsible Business Base.
The docopt module is a doctest-like approach where the command-line input specification is simply specified in the documentation (i.e., the docstring) of the script, just as you write the ordinary documentation. The simplicity in the approach may best be described by citing a YouTube comment: "holy shit".
#!/usr/bin/env python """ mydocopter. Usage: mydocopter [options] <filename> Options: -v --verbose Log messages -o OUTPUT --output=OUTPUT Output file -a <a> Initial coefficient for second order term [default: 1.] -b <b> Initial coefficient for first order term [default: 1.] -c <c> Initial coefficient for constant term [default: 1.] Example: $ echo -e "1 4\\n2 5\\n6 8\\n3 3.2" > datafile.txt $ ./mydocopter --verbose datafile.txt 0.315471154631 -1.51271481921 5.64476836068 $ ./mydocopter -o p.txt datafile.txt $ ipython --pylab --c="m=loadtxt('datafile.txt'); p=loadtxt('p.txt'); x=linspace(1,6); plot(m[:,0], m[:,1], 'o', x, p[0]*x**2+p[1]*x+p[2], '-'); raw_input()" Description: Fit a polynomial to data. The datafile should have x y values in each row """ import docopt, logging, scipy.optimize args = docopt.docopt(__doc__, version=1.0) if args['--verbose']: logging.getLogger().setLevel(logging.INFO) a, b, c = (float(args['-' + coef]) for coef in ['a', 'b', 'c']) logging.info("Setting 'a' to %f" % a) logging.info('Reading data from ' + args['<filename>']) data = [ map(float, line.split()) for line in open(args['<filename>']).readlines()] def cost_function((a, b, c), data): return sum(map(lambda (x, y): (a*x**2 + b*x + c - y)**2, data)) parameters = scipy.optimize.fmin(cost_function, [a, b, c], args=(data,), disp=False) if args['--output'] is None: print(" ".join(map(str, parameters))) else: with open(args['--output'], 'w') as f: f.write(" ".join(map(str, parameters)))
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