Ok, long story: I'm trying to solve level 4 of the Python Challenge. I
hate to post here, but the hint forum over there is dead. Here's the
link: http://www.pythonchallenge.com/pc/def/linkedlist.php
Apparently you need to use a linked list to solve it, so I read up on
them but I still don't understand how to implement one to solve this
problem. (Any hints there would be appreciated too.) So I wrote this
code instead. It goes to each URL, reads the source code, gets the next
number, etc. I realize it uses some terrible tricks, like the regex and
the try/except clause, which is way too specific to solve the problem in
a general way. Anyway, here's the code:
# Python Challenge, level 4
import urllib
import re
url = 'http://www.pythonchall enge.com/pc/def/linkedlist.php? nothing='
pattern = re.compile(r'\b next nothing is (\d+)')
def getNextNum(url) :
global pattern
global nextNum
site = urllib.urlopen( url)
try:
source = site.read()
site.close()
number = re.search(patte rn, source).group(1 )
except:
print nextNum
number = str(int(nextNum ) / 2)
return number
nextNum = '12345'
f = open(r'C:\Pytho n24\myscripts\c hallenges\numbe rs.txt', 'w')
try:
for x in range(300):
f.write(nextNum + '\n')
nextNum = getNextNum(url + nextNum)
finally:
f.close()
print url + nextNum
Now, I tried this earlier on my work computer and it got as far as
printing out two 'nextNum's in the except block, then it appeared that
the website timed out and I could no longer access it for a while.
I tried later on my home computer and now I keep getting this error:
Traceback (most recent call last):
File "C:\Python24\my scripts\challen ges\linked_list .py", line 27, in
-toplevel-
nextNum = getNextNum(url + nextNum)
File "C:\Python24\my scripts\challen ges\linked_list .py", line 12, in
getNextNum
site = urllib.urlopen( url)
File "C:\Python24\li b\urllib.py", line 82, in urlopen
return opener.open(url )
File "C:\Python24\li b\urllib.py", line 190, in open
return getattr(self, name)(url)
File "C:\Python24\li b\urllib.py", line 322, in open_http
return self.http_error (url, fp, errcode, errmsg, headers)
File "C:\Python24\li b\urllib.py", line 339, in http_error
return self.http_error _default(url, fp, errcode, errmsg, headers)
File "C:\Python24\li b\urllib.py", line 579, in http_error_defa ult
return addinfourl(fp, headers, "http:" + url)
File "C:\Python24\li b\urllib.py", line 871, in __init__
addbase.__init_ _(self, fp)
File "C:\Python24\li b\urllib.py", line 818, in __init__
self.read = self.fp.read
AttributeError: 'NoneType' object has no attribute 'read'
I didn't get this before, so I wonder if it's a website error. There
seems to be a problem with getting the source code. It also appears that
the script, when run at home, doesn't get as far as the same script when
I ran it earlier today at work.
So I figure it's either a website problem, or some kind of strange
difference between the two computers I'm using (but both use 2.4.3 and
nothing else seems different).
I hope someone can point me in the right direction. I'm curious why it
fails in a different way at home than at work, but also I'd like to know
if it's even possible to solve the problem in this way, or if I *have*
to use a linked list.
hate to post here, but the hint forum over there is dead. Here's the
link: http://www.pythonchallenge.com/pc/def/linkedlist.php
Apparently you need to use a linked list to solve it, so I read up on
them but I still don't understand how to implement one to solve this
problem. (Any hints there would be appreciated too.) So I wrote this
code instead. It goes to each URL, reads the source code, gets the next
number, etc. I realize it uses some terrible tricks, like the regex and
the try/except clause, which is way too specific to solve the problem in
a general way. Anyway, here's the code:
# Python Challenge, level 4
import urllib
import re
url = 'http://www.pythonchall enge.com/pc/def/linkedlist.php? nothing='
pattern = re.compile(r'\b next nothing is (\d+)')
def getNextNum(url) :
global pattern
global nextNum
site = urllib.urlopen( url)
try:
source = site.read()
site.close()
number = re.search(patte rn, source).group(1 )
except:
print nextNum
number = str(int(nextNum ) / 2)
return number
nextNum = '12345'
f = open(r'C:\Pytho n24\myscripts\c hallenges\numbe rs.txt', 'w')
try:
for x in range(300):
f.write(nextNum + '\n')
nextNum = getNextNum(url + nextNum)
finally:
f.close()
print url + nextNum
Now, I tried this earlier on my work computer and it got as far as
printing out two 'nextNum's in the except block, then it appeared that
the website timed out and I could no longer access it for a while.
I tried later on my home computer and now I keep getting this error:
Traceback (most recent call last):
File "C:\Python24\my scripts\challen ges\linked_list .py", line 27, in
-toplevel-
nextNum = getNextNum(url + nextNum)
File "C:\Python24\my scripts\challen ges\linked_list .py", line 12, in
getNextNum
site = urllib.urlopen( url)
File "C:\Python24\li b\urllib.py", line 82, in urlopen
return opener.open(url )
File "C:\Python24\li b\urllib.py", line 190, in open
return getattr(self, name)(url)
File "C:\Python24\li b\urllib.py", line 322, in open_http
return self.http_error (url, fp, errcode, errmsg, headers)
File "C:\Python24\li b\urllib.py", line 339, in http_error
return self.http_error _default(url, fp, errcode, errmsg, headers)
File "C:\Python24\li b\urllib.py", line 579, in http_error_defa ult
return addinfourl(fp, headers, "http:" + url)
File "C:\Python24\li b\urllib.py", line 871, in __init__
addbase.__init_ _(self, fp)
File "C:\Python24\li b\urllib.py", line 818, in __init__
self.read = self.fp.read
AttributeError: 'NoneType' object has no attribute 'read'
I didn't get this before, so I wonder if it's a website error. There
seems to be a problem with getting the source code. It also appears that
the script, when run at home, doesn't get as far as the same script when
I ran it earlier today at work.
So I figure it's either a website problem, or some kind of strange
difference between the two computers I'm using (but both use 2.4.3 and
nothing else seems different).
I hope someone can point me in the right direction. I'm curious why it
fails in a different way at home than at work, but also I'd like to know
if it's even possible to solve the problem in this way, or if I *have*
to use a linked list.
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