getting arguments from command line python

Question

I am trying to get three arguments from command line:

-o (for outputfile) -k (number of clusters) -l (data to be clustered)

So i wrote this.

def get_input():
print 'ARGV :', sys.argv[1:]
options, remainder = getopt.getopt(sys.argv[1:], 'o:v:k:l', ['output=', 
 'verbose',
 'k_clust=',
 'limit='])
print "options ",options
file_flag , k_flag, count_flag = False, False,False
for opt, arg in options:
 print opt
 if opt in ('-o', '--output'):
 print "here ", opt, arg
 output_filename = arg
 o_flag = True
 if opt in ('-v', '--verbose'):
 verbose = True
 if opt == '--version':
 version = arg
 if opt in ('-k','--k_clust'):
 print "here", opt, arg
 k_clust = arg
 k_flag = True
 if opt in ('-l','--limit'):
 kcount = arg
 assert kcount!=0 and kcount!= ''
 print "limit ", arg
 count_flag = True
if k_flag == False:
 sys.exit(" no cluster specified, will be exiting now")
if o_flag == False:
 print "using default outfile name ",output_filename
if count_flag == False:
 kcount = 10000000
return output_filename, k_clust,kcount

Everything is working on fine except the -l flag so if my command line command is this:

$python foo.py -o foo.txt -k 2 -l 2

and the print argv prints

ARGV : ['-o', 'demo.txt', '-k', '2', '-l', '2']

but the options is:

options [('-o', 'demo.txt'), ('-k', '2'), ('-l', '')]

Notice that nothing is being parsed in the "l" field. Wat am i doing wrong? Thanks

Answer 1

getopt is a rather old module. If you have Python2.7, use argparse. If you have a slightly older version of Python>= 2.3, you can still install argparse:

With

import argparse
parser=argparse.ArgumentParser()
parser.add_argument('-o', help = 'outputfile')
parser.add_argument('-k', help = 'number of clusters')
parser.add_argument('-l', help = 'data to be clustered')
args=parser.parse_args()
print(args)

running

test.py -o foo.txt -k 2 -l 2

yields

Namespace(k='2', l='2', o='foo.txt')

Answer 2

It's because in your shortopts parameter: 'o:v:k:l', the "l" needs to be followed by a colon ":"

Since it's not, the "2" is being put into the remainder variable.