Python: urllib.error.HTTPError: HTTP Error 404: Not Found

Question

I wrote a script to find spelling mistakes in SO questions' titles. I used it for about a month.This was working fine.

But now, when I try to run it, I am getting this.

Traceback (most recent call last):
  File "copyeditor.py", line 32, in <module>
    find_bad_qn(i)
  File "copyeditor.py", line 15, in find_bad_qn
    html = urlopen(url)
  File "/usr/lib/python3.4/urllib/request.py", line 161, in urlopen
    return opener.open(url, data, timeout)
  File "/usr/lib/python3.4/urllib/request.py", line 469, in open
    response = meth(req, response)
  File "/usr/lib/python3.4/urllib/request.py", line 579, in http_response
    'http', request, response, code, msg, hdrs)
  File "/usr/lib/python3.4/urllib/request.py", line 507, in error
    return self._call_chain(*args)
  File "/usr/lib/python3.4/urllib/request.py", line 441, in _call_chain
    result = func(*args)
  File "/usr/lib/python3.4/urllib/request.py", line 587, in http_error_default
    raise HTTPError(req.full_url, code, msg, hdrs, fp)
urllib.error.HTTPError: HTTP Error 404: Not Found

This is my code

import json
from urllib.request import urlopen
from bs4 import BeautifulSoup
from enchant import DictWithPWL
from enchant.checker import SpellChecker

my_dict = DictWithPWL("en_US", pwl="terms.dict")
chkr = SpellChecker(lang=my_dict)
result = []


def find_bad_qn(a):
    url = "https://stackoverflow.com/questions?page=" + str(a) + "&sort=active"
    html = urlopen(url)
    bsObj = BeautifulSoup(html, "html5lib")
    que = bsObj.find_all("div", class_="question-summary")
    for div in que:
        link = div.a.get('href')
        name = div.a.text
        chkr.set_text(name.lower())
        list1 = []
        for err in chkr:
            list1.append(chkr.word)
        if (len(list1) > 1):
            str1 = ' '.join(list1)
            result.append({'link': link, 'name': name, 'words': str1})


print("Please Wait.. it will take some time")
for i in range(298314,298346):
    find_bad_qn(i)
for qn in result:
    qn['link'] = "https://stackoverflow.com" + qn['link']
for qn in result:
    print(qn['link'], " Error Words:", qn['words'])
    url = qn['link']

UPDATE

This is the url causing the problem.Even though this url exists.

https://stackoverflow.com/questions?page=298314&sort=active

I tried changing the range to some lower values. It works fine now.

Why this happened with above url?

Answer 1

So apparently the default display number of questions per page is 50 so the range you defined in the loop goes out of the available number of pages with 50 questions per page. The range should be adapted to be within the number of total pages with 50 questions each.

This code will catch the 404 error which was the reason you got an error and ignore it just in case you go out of the range.

from urllib.request import urlopen

def find_bad_qn(a):
    url = "https://stackoverflow.com/questions?page=" + str(a) + "&sort=active"
    try:
        urlopen(url)
    except:
        pass

print("Please Wait.. it will take some time")
for i in range(298314,298346):
    find_bad_qn(i)