Question

I want to pass 4 arguments to my python script and one of them has to be a list. Even if it just contains 1 element.

The order of the arguments does not matter.

    import sys
    print sys.argv

    one = sys.argv[1]
    two = sys.argv[2]
    three = sys.argv[3]
    four = sys.argv[4]

    print "one: " + one
    print "two: " + two
    print "three: "+ three
    print "four: " + four

This is how I am calling it.

    python myScript.py name file setting ['listItem1']

Where the fourth item is the list with one element. However when I print it I see

    four: [listItem1]

I would like to see

    four: ['listItem1']

Answer 1

as PersonArtPhoto pointed out, you need to escape the qutoation marks to prevent the shell from using them itself.

What you’re going to wind up with in your program is a string that resembles a list, which isn’t what you want

import sys 

four = sys.argv[4]
print four[2]

shows

$ python myscript.py one two three [\'first\',\'second\']
f

this 'f' is coming from indexing "['first','second']" because it is just a string of characters

---

one way to make python interpret this is eval but it is highly discouraged as it is extremely insecure. eval interprets a string as code, so it shouldn’t be used on user input because the user can enter anything and python will execute it.

import sys 

four = eval(sys.argv[4])
print four[1]

shows

$ python myscript.py one two three [\'first\',\'second\']
second

---

instead I suggest a safer approach. Use a command line flag to signal that you are sending the list of arguments

import sys

# make sure the --args flag was passed
if '--args' not in sys.argv:
    print >> sys.stderr, 'Please pass the "--args" flag followed by a list of'\
            ' arguments'
    sys.exit(1) #terminate execution if it wasn't

four = sys.argv[sys.argv.index('--args')+1:] # everything passed after --args
print four

shows

$ python myscript.py one two three --args 'first' 'second'
['first', 'second']

---

if you know that there will always be three args before your list, you can simply use a slice

import sys

one, two, three = sys.argv[1:4] # grab indicies 1, 2, and 3
four = sys.argv[4:]
print one
print two
print three
print four

shows

$ python myscript.py one two three 'first' 'second'
one
two
three
['first', 'second']