需要弄清楚为什么我的Python程序不起作用（排序-按字母顺序排列）

Question

The instructions were to: Write a Python program that reads in an two or more strings from the command line and displays them sorted alphabetically. Basic Requirements - Validate inputs - Proper error handling - Sorts two or or more words passed as program arguments - Correct documentation - Proper documentation mean that the top of the file should contain your name, the program's name, the purpose of the program and an example invocation of the program. Also documentation complex or confusing lines in your code. However, there should not be too many of those.

My code:

# mySorter.py. 
# This program reads two or more strings as program
# arguments and displays them sorted.
# Program will sort alphabetically the words from a string provided by the 
user
# Take input from the user
my_str = input("Enter a string: ")

# breakdown the string into a list of words
words = my_str.split()

# sort the list
words.sort()

for word in words:
print(word)

if len(my_str.split()) < 2:
print("Please provide more than one word.")

Apparently, I am doing something wrong. I was told that This program does not meet the requirements. It has to read arguments passed to the program when the program is started.Any suggestions? Thanks.

Answer 1

# mySorter.py. 
# This program reads two or more strings as program
# arguments and displays them sorted.
# Program will sort alphabetically the words from a string provided by the user

# Simply run this program as follows:
# python your_script.py "hello user"

import argparse

argparser = argparse.ArgumentParser()
argparser.add_argument('my_str',help = 'User string')
args = argparser.parse_args()
if args.my_str:
    my_str = args.my_str

    # breakdown the string into a list of words
    words = my_str.split()

    if len(words) <= 1:
        print("Please provide more than one word.")
    else:
        # sort the list
        words.sort()

        for word in words:
            print(word)
else:
    print('No words to sort!')
    print('Try the following: python my_script.py "hello world"')

The requirement of "It has to read arguments passed to the program when the program is started." to me, tells me you need to use argparser to send a string without being prompted by an input(). Which explains why you aren't meeting it, since you aren't currently doing this :-)

Answer 2

I was told that This program does not meet the requirements. It has to read arguments passed to the program when the program is started

Instead of using input() to prompt the user for strings, I think they want you to use something like sys.argv to get the list of input strings that you need to sort from the command line, eg python myscript.py str1 str2 str3 .

Slightly modified for python3 from https://www.tutorialspoint.com/python/python_command_line_arguments.htm , put the following into a "test.py" file:

import sys

print('Number of arguments: {} arguments'.format(len(sys.argv)))
print('Argument List: {}'.format(sys.argv))

At the command line, do:

python test.py arg1 arg2 arg3

This produces the following result:

Number of arguments: 4 arguments.
Argument List: ['test.py', 'arg1', 'arg2', 'arg3']

To get the arguments excluding the script name, you can do something like words = sys.argv[1:] . This will return a list of arguments starting with the second one. You can then go ahead and sort your list as per your original program.