sys.argv列表索引超出范围错误

Question

我正在尝试运行在“ Thonny”环境中获取rss feed的脚本，但是我一直收到以下错误：“ IndexError：列表索引超出范围”

Traceback (most recent call last):
File "C:\Users\uri\rssfeedfour.py", line 11, in <module>
url = sys.argv[1]
IndexError: list index out of range

我如何解决此问题，以免一遍又一遍地出现此错误。 我不知道该如何解决这个问题，因为我是新手。 我是否需要定义它（如果这样）？ 还是我可以将其取出并朝另一个方向走？ 这是代码。

import feedparser
import time
from subprocess import check_output
import sys

#feed_name = 'TRIBUNE'
#url = 'http://chicagotribune.feedsportal.com/c/34253/f/622872/index.rss'

feed_name = sys.argv[1]
url = sys.argv[2]

db = 'http://feeds.feedburner.com/TheHackersNews'
limit = 12 * 3600 * 1000

current_time_millis = lambda: int(round(time.time() * 1000))
current_timestamp = current_time_millis()

def post_is_in_db(title):
    with open(db, 'r') as database:
        for line in database:
            if title in line:
                return True
    return False


def post_is_in_db_with_old_timestamp(title):
    with open(db, 'r') as database:
        for line in database:
            if title in line:
                ts_as_string = line.split('|', 1)[1]
                ts = long(ts_as_string)
                if current_timestamp - ts > limit:
                    return True
    return False

#
# get the feed data from the url
#
feed = feedparser.parse(url)

#
# figure out which posts to print
#
posts_to_print = []
posts_to_skip = []

for post in feed.entries:
    # if post is already in the database, skip it
    # TODO check the time
    title = post.title
    if post_is_in_db_with_old_timestamp(title):
        posts_to_skip.append(title)
    else:
        posts_to_print.append(title)

#
# add all the posts we're going to print to the database with the current timestamp
# (but only if they're not already in there)
#
f = open(db, 'a')
for title in posts_to_print:
    if not post_is_in_db(title):
        f.write(title + "|" + str(current_timestamp) + "\n")
f.close

#
# output all of the new posts
#
count = 1
blockcount = 1
for title in posts_to_print:
    if count % 5 == 1:
        print("\n" + time.strftime("%a, %b %d %I:%M %p") + '  ((( ' + feed_name + ' - ' + str(blockcount) + ' )))')
        print("-----------------------------------------\n")
        blockcount += 1
    print(title + "\n")
    count += 1

Answer 1

sys.argv是Python中的列表，其中包含传递给脚本的命令行参数。 sys.argv[0]包含脚本的名称， sys.argv[1]包含第一个参数，依此类推。

为防止此错误，启动脚本时需要提供命令行参数。 例如，您可以通过以下方式启动此脚本，而不会出现任何错误：

python rssfeedfour.py TRIBUNE http://chicagotribune.feedsportal.com/c/34253/f/622872/index.rss

您也可以修改脚本，以便在不提供任何命令行参数的情况下使用默认参数来工作。

try:
    feed_name = sys.argv[1]
except IndexError:
    feed_name = 'TRIBUNE'

try: 
    url = sys.argv[2]
except IndexError:
    url = 'http://chicagotribune.feedsportal.com/c/34253/f/622872/index.rss'

您可以在此处了解有关处理错误的更多信息。

尽管使用argparse库要方便得多。