Passing a List to Python From Command Line

Question

I would like to make my python script run from the command line when supplies with some arguments. However, one of the arguments should be a list of options specific to one segment of the script. Would string parsing be the only way to do this by actually constructing the list after the "command line list" string is split from commas? If so, how would you go about that?

Example: -details=['name', 'title', 'address']

Answer 1

Program:

import sys, ast, getopt, types

def main(argv):            
    arg_dict={}
    switches={'li':list,'di':dict,'tu':tuple}
    singles=''.join([x[0]+':' for x in switches])
    long_form=[x+'=' for x in switches]
    d={x[0]+':':'--'+x for x in switches}
    try:            
        opts, args = getopt.getopt(argv, singles, long_form)
    except getopt.GetoptError:          
        print "bad arg"                       
        sys.exit(2)       

    for opt, arg in opts:        
        if opt[1]+':' in d: o=d[opt[1]+':'][2:]
        elif opt in d.values(): o=opt[2:]
        else: o =''
        print opt, arg,o
        if o and arg:
            arg_dict[o]=ast.literal_eval(arg)

        if not o or not isinstance(arg_dict[o], switches[o]):    
            print opt, arg, " Error: bad arg"
            sys.exit(2)                 

    for e in arg_dict:
        print e, arg_dict[e], type(arg_dict[e])        

if __name__ == '__main__':
    main(sys.argv[1:])        

Command line:

python py.py --l='[1,2,3,[1,2,3]]' -d "{1:'one',2:'two',3:'three'}" --tu='(1,2,3)'

Output:

args:  ['--l=[1,2,3,[1,2,3]]', '-d', "{1:'one',2:'two',3:'three'}", '--tu=(1,2,3)']
tu (1, 2, 3) <type 'tuple'>
di {1: 'one', 2: 'two', 3: 'three'} <type 'dict'>
li [1, 2, 3, [1, 2, 3]] <type 'list'>

This code snippet will take short or long command switches like -l or --li= and parse the text after the switch into a Python data structure like a list, tuple or a dict. The parsed data structure ends up in a dictionary with the long-form switch key.

Using ast.literal_eval is relatively safe. It can only parse python data definitions.