如何修复“列表索引必须为整数或切片”错误

Question

I'm making a program that should save your ip address to a list in a separate file using shelve. Each time it is opened it should put the the ip address in list "pubipcount" in list "pubiplist". When I go to add a new ip I get an error that I don't understand.

I've only ran the code bit by bit to find the part that is broken, and I've taken the liberty of narrowing it down to only the information you need to help me. I've already looked online for a possible answer but I haven't found anything helpful to me.

import shelve
import socket
import urllib.request

save = shelve.open('ip_whitelist', writeback=True)

hostname = socket.gethostname()
PubIP = urllib.request.urlopen('https://ident.me').read().decode('utf8')
LocIP = socket.gethostbyname(hostname)

save['pubipcount'] = 0
save['pubiplist'] = []

save['pubipcount'] = save['pubipcount'] + 1
save['pubiplist']['pubipcount'] = PubIP

This is the exact error:

Traceback (most recent call last):
  File "C:\Users\brenn\Desktop\IP\ip.py", line 27, in <module>
    save['pubiplist']['pubipcount'] = PubIP
TypeError: list indices must be integers or slices, not str

Answer 1

The problem is ['pubipcount'] . In the context it is just a string. I believe you want:

save['pubiplist'][save['pubipcount']] = PubIP

This way you are referring to the value in save['pubipcount'] instead of the string 'pubipcount' as the index.

Edit: This will likely result in an IndexError, so using append() is better

save['pubiplist'].append(PubIP)

Answer 2

if you use a list the index must be integers such as save['pubiplist'][0]

if you want a str as key, you can use a dict instead, change save['pubiplist'] = [] to save['pubiplist'] = {}

---

for your situation, I suggest you to use PubIP as key, and count PubIP separately:

from collections import defaultdict
# do this only once
save['pubiplist'] = defaultdict(int)

# recieve IP repeately

# update IP and count each time
save['pubiplist'][PubIP] += 1

Answer 3

Shelve allows you use strings as keys but you can't use them as sub-indexes.

The quickest fix would be to interpolate the count into the key:

save[f'pubiplist-{pubipcount}'] = PubIP