The loop over m

Cannot use

for m in range(m_min, m_max, dm):

because range works with integers only

A while-loop is appropriate:

m = m_min
while m <= m_max:
    case = 'tmp_m_%g' % m
    s = 'python simviz1.py %s -m %g -case %s' % \
        (simviz1_options, m, case)
    failure, output = commands.getstatusoutput(s)
    m += dm

(Note: our -m and -case will override any -m or -case option provided by the user)