Passing meta-characters to Python as arguments from command line

Question

I\'m making a Python program that will parse the fields in some input lines. I\'d like to let the user enter the field separator as an option from the command line. I\'m usi

Answer 1

The callback option is a good way to handle tricky cases:

parser.add_option("-d", "--delimiter", action="callback", type="string",
                  callback=my_callback, default='\t')

with the corresponding function (to be defined before the parser, then):

def my_callback(option, opt, value, parser):
    val = value
    if value == '\\t':
        val = '\t'
    elif value == '\\n':
        val = '\n'
    parser.values.delimiter = val

You can check this works via the command line: python test.py -f test.txt -d \t (no quote around the \t, they're useless).

It has the advantage of handling the option via the 'optparse' module, not via post-processing the parsing results.