Passing a List to Python From Command Line

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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.

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