Python - Understanding error: IndexError: list index out of range

Question

I'm fairly new to python. I have an error that I need to understand.

The code:

config.py:

# Vou definir os feeds
feeds_updates = [{"feedurl": "http://aaa1.com/rss/punch.rss", "linktoourpage": "http://www.ha.com/fun.htm"},
                 {"feedurl": "http://aaa2.com/rss.xml", "linktoourpage": "http://www.ha.com/fun.htm"},
                 {"feedurl": "http://aaa3.com/Heaven", "linktoourpage": "http://www.ha.com/fun.htm"},
                 {"feedurl": "http://aaa4.com/feed.php", "linktoourpage": "http://www.ha.com/fun.htm"},
                 {"feedurl": "http://aaa5.com/index.php?format=feed&type=rss", "linktoourpage": "http://www.ha.com/fun.htm"},
                 {"feedurl": "http://aaa6.com/rss.xml", "linktoourpage": "http://www.ha.com/fun.htm"},
                 {"feedurl": "http://aaa7.com/?format=xml", "linktoourpage": "http://www.ha.com/fun.htm"},
                 {"feedurl": "http://aaa8/site/component/rsssyndicator/?feed_id=1", "linktoourpage": "http://www.ha.com/fun.htm"}]

twitterC.py

# -*- coding: utf-8 -*-
import config   # Ficheiro de configuracao
import twitter
import random
import sqlite3
import time
import bitly_api #https://github.com/bitly/bitly-api-python
import feedparser

...

# Vou escolher um feed ao acaso
feed_a_enviar = random.choice(config.feeds_updates)
# Vou apanhar o conteudo do feed
d = feedparser.parse(feed_a_enviar["feedurl"])
# Vou definir quantos feeds quero ter no i
i = range(8)
print i
# Vou meter para "updates" 10 entradas do feed
updates = []
for i in range(8):
    updates.append([{"url": feed_a_enviar["linktoourpage"], "msg": d.entries[i].title + ", "}])
# Vou escolher ums entrada ao acaso
print updates # p debug so
update_to_send = random.choice(updates)

print update_to_send # Para efeitos de debug

And the error that appears sometimes because of the nature of the random:

Traceback (most recent call last):
  File "C:\Users\anlopes\workspace\redes_sociais\src\twitterC.py", line 77, in <module>
    updates.append([{"url": feed_a_enviar["linktoourpage"], "msg": d.entries[i].title + ", "}])
IndexError: list index out of range

I'am not getting to the error, the list "feeds_updates" is a list with 8 elements, I think is well declareted and the RANDOM will choose one out of the 8...

Can someone give me a clue on what is happenning here?

PS: Sorry for my bad english.

Best Regards,

Solution 1

Using range for iteration is nearly always not the best way. In Python you can iterate directly over a list, dict, set etc.:

for item in d.entries:
    updates.append([{"url": feed_a_enviar["linktoourpage"], "msg": item.title + ", "}])

Obviously d.entries[i] triggers the error because that list contains less than 8 items (feeds_updates may contain 8, but you are not iterating over that list).

Solution 2

d.entries has less than 8 elements. Iterate over d.entries directly instead of some disconnected range.

Comments

[user1066101]

You are aware that indexes start at zero? 8 elements have indexes 0 to 7?

[Tim Pietzcker]

@S. Lott: And range(8) is [0,1,2,3,4,5,6,7], so that's not the problem here.

[user1066101]

@Tim Pietzcker: Of course, we're both assuming that the code which was presented actually has 8 items in the feed_updates list, aren't we? Yes, the evidence is good, but there has to be something going on that's not shown in the code snippet provided.

[Tim Pietzcker]

@S. Lott: The number of items in feed_updates is irrelevant because he's iterating over a completely different list. See my answer.