Using Optparse and Writing output to named files

Question

I'm trying to write a script which will take in a parameter beta, and a number of iterations k, and then print "beta" k times.

I want to be able to specify beta and k at the command line, and then run this script from there. I've been using optparse as follows:

import io
from optparse import OptionParser

parser = OptionParser()
parser.add_option("-b", "--beta",type="float", dest="input_parameter")
parser.add_option("-k", "-iterations",type="int",dest="number_of_iterations")

(options, args) = parser.parse_args()

Beta = options.input_parameter
K = options.number_of_iterations

with io.open("output_when_beta_equals_{0}.txt".format(Beta), "a") as f:
    for i in range(K):
        f.write(u"beta = {0}, this is iteration number {1}.".format(Beta, i))

I then try to run

python toy_script.py -b $"0.3" -k $20

from the command line, and then the resulting "output_when_beta_equals_0.3.txt" file ends up empty.

I'm trying to work out what I need to do to fix this so that I instead get 20 lines of

beta = 0.3, this is iteration number 0. beta = 0.3, this is iteration number 1.

.... etc., in the output file.

Answer 1

Your code works, after replacing -iterations by --iterations and calling it like this:

python toy_script.py -b0.3 -k20

(tested on Windows)