argparse-assign list items to variables

Question

I want to pass multiple arguments using cmd to the python script. below is the code I have used.

import argparse

ap = argparse.ArgumentParser()
ap.add_argument('-n', '--names-list', nargs='+', default=[])  
#item1 item2 item3 item4
args = vars(ap.parse_args())

a = args.names-list[0]
b= args.names-list[1]
c=args.names-list[2]
d=args.names-list[3]

print(a)
print(b)
print(c)
print(d)

when I execute the code I got an error message like below.

File "D:\script.py", line 7, in <module>
a = args.names-list[0]
AttributeError: 'dict' object has no attribute 'names'

as I'm very new to this, can somebody help me to solve the problem?

See the dupe target: `a = args.names-list[0]` is actually `a = args.names - list[0]`. What you want is `a = args.names_list[0]` — TemporalWolf, May 25 '18 at 20:14
I disagree that this is a dupe. OP has multiple errors, only one of which is resolved by the duplicate. — Robᵩ, May 25 '18 at 20:20
@Robᵩ While true, the dupe target also shows the proper usage of parse_args and the dupe does address the specific question asked/error encountered. The answer you wrote is still helpful to the OP I'm sure, but future readers will likely be better served via the dupe. — TemporalWolf, May 25 '18 at 20:34
When debugging `argparse` it helps to `print(args)` (even before use `vars`). That will show all the attributes, their correct names, and values. — hpaulj, May 25 '18 at 20:43

score 1 · Accepted Answer · answered May 25 '18 at 20:14

1

This line is incorrect. You do not need to invoke vars().

args = vars(ap.parse_args())

Instead, try this:

args = ap.parse_args()

Additionally, the argument names are automatically translated from using - to using _. Try this: a = args.names_list[0]

Here is your program, with corrections:

import argparse

ap = argparse.ArgumentParser()
ap.add_argument('-n', '--names-list', nargs='+', default=[])
#item1 item2 item3 item4
args = ap.parse_args()

a = args.names_list[0]
b= args.names_list[1]
c=args.names_list[2]
d=args.names_list[3]

print(a)
print(b)
print(c)
print(d)

And here is the result:

$ python x.py -n one two three four
one
two
three
four

answered May 25 '18 at 20:14

Robᵩ

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I got an error like this. a = args.names-list[0] AttributeError: 'Namespace' object has no attribute 'names' – jemma ferdinas May 25 '18 at 20:18
1

You should use `args.names_list`, not `args.names-list`. – Robᵩ May 25 '18 at 20:19
it shows an error message of `list index out of range` – jemma ferdinas May 25 '18 at 20:23
If you don't supply 4 arguments it will say that: `args.names_list` is only as long as the number of items you've put in it. – TemporalWolf May 25 '18 at 20:30
It's also worth mentioning if you want to force them to supply exactly 4 arguments, you can use `nargs=4` rather than `nargs='+'` – TemporalWolf May 25 '18 at 20:37

argparse-assign list items to variables

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