Question

Let me start off by saying, I’m not new to programming but am very new to python.

I’ve written a program using urllib2 that requests a web page that I would then like to save to a file. The web page is about 300KB, which doesn’t strike me as particularly large but seems to be enough to give me trouble, so I’m calling it ‘large’.
I’m using a simple call to copy directly from the object returned from urlopen into the file:

file.write(webpage.read())

but it will just sit for minutes, trying to write into the file and I eventually receive the following:

Traceback (most recent call last):
  File "program.py", line 51, in <module>
    main()
  File "program.py", line 43, in main
    f.write(webpage.read())
  File "/usr/lib/python2.7/socket.py", line 351, in read
    data = self._sock.recv(rbufsize)
  File "/usr/lib/python2.7/httplib.py", line 541, in read
    return self._read_chunked(amt)
  File "/usr/lib/python2.7/httplib.py", line 592, in _read_chunked
    value.append(self._safe_read(amt))
  File "/usr/lib/python2.7/httplib.py", line 649, in _safe_read
    raise IncompleteRead(''.join(s), amt)
httplib.IncompleteRead: IncompleteRead(6384 bytes read, 1808 more expected)

I don’t know why this should give the program so much grief?

---

EDIT |

here is how I’m retrieving the page

jar = cookielib.CookieJar()

cookie_processor = urllib2.HTTPCookieProcessor(jar);

opener = urllib2.build_opener(cookie_processor)
urllib2.install_opener(opener)

requ_login = urllib2.Request(LOGIN_PAGE,
                             data = urllib.urlencode( { 'destination' : "", 'username' : USERNAME, 'password' :  PASSWORD } ))

requ_page = urllib2.Request(WEBPAGE)    
try:
    #login
    urllib2.urlopen(requ_login)

    #get desired page
    portfolio = urllib2.urlopen(requ_page)
except urllib2.URLError as e:
    print e.code, ": ", e.reason

Answer 1

I’d use a handy fileobject copier function provided by shutil module. It worked on my machine 🙂

>>> import urllib2
>>> import shutil
>>> remote_fo = urllib2.urlopen('http://docs.python.org/library/shutil.html')
>>> with open('bigfile', 'wb') as local_fo:
...     shutil.copyfileobj(remote_fo, local_fo)
... 
>>> 

UPDATE: You may want to pass the 3rd argument to copyfileobj that controls the size of internal buffer used to transfer bytes.

UPDATE2: There’s nothing fancy about shutil.copyfileobj. It simply reads a chunk of bytes from source file object and writes it the destination file object repeatedly until there’s nothing more to read. Here’s the actual source code of it that I grabbed from inside Python standard library:

def copyfileobj(fsrc, fdst, length=16*1024):
    """copy data from file-like object fsrc to file-like object fdst"""
    while 1:
        buf = fsrc.read(length)
        if not buf:
            break
        fdst.write(buf)