在for循环中使用argparse add_argument

Question

I am trying to use parser.add_argument in a for loop but am getting an error. Following is my sample code and error. Any help is appreciated.Thanks!

---

Am using an itemlist file in my example.It is a plain file with items listed in it as follows:

item1
item2
item3

---

test.py contains the following code

#!/usr/bin/python

import re
import os
import string
import argparse

parser = argparse.ArgumentParser()

itemlist = open("itemlist").read().splitlines()
for item in itemlist:
  print(item)
  parser.add_argument(item)

version=parser.parse_args()
for item in itemlist:
  print(getattr(version,item))

---

Running the script as ./test.py 1.00 2.00 3.00

Am expecting the output to be

1.00
2.00
3.00

Error on running the program :

 parser.add_argument(item)
  File "/usr/local/lib/python3.4/argparse.py",
    if not args or len(args) == 1 and args[0][0] not in chars:
IndexError: string index out of range

This works if I just have one item. It does not work if I have more than one item. What is that am doing wrong ?

Answer 1

You have an empty line at the end of the file.

I tested it and it worked fine (with python 3.4.3). After adding an empty line at the end of itemlist it fails with that error.

Edit: I've just checked argparse source code and it seems that args holds [""] when the empty line is read. So if you execute that in your console:

>>> [""][0][0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: string index out of range