An error was introduced in 2.6.6 rc1 in the socket flush() call where del is called on the unbound 'view' variable.

Associated commit and diff:

http://svn.python.org/view?view=rev&revision=83624
http://svn.python.org/view/python/tags/r266rc1/Lib/socket.py?r1=81488&r2=83624

Tail end of the runtime stack trace:

  File "/usr/lib/python2.6/socket.py", line 318, in write
    self.flush()
  File "/usr/lib/python2.6/socket.py", line 302, in flush
    del view, data  # explicit free
UnboundLocalError: local variable 'view' referenced before assignment

Thank you very much for testing the alpha and making a report.  I've added Ezio to nosy since he backported the patch, and Barry since he's release manager.

Thanks for the report and for figuring out what was the cause!
Indeed the "view" added after the "del" shouldn't be there, so I will remove it.
It would also be great if you could provide a minimal script to reproduce the problem so that it can be turned to a test. None of the tests in the current test suite seem to go through that code path, so the error passed unnoticed.

spiv wrote a script to repo the issue in the downstream ubuntu bug:
https://bugs.launchpad.net/python/+bug/615240

I have a reproduction script on the Ubuntu bug report I just filed for this issue: <https://bugs.launchpad.net/ubuntu/+source/python2.6/+bug/615240>

Pasting here for convenience:

"""
import socket
import threading

sock_a, sock_b = socket.socketpair()
sock_a = socket.socket(_sock=sock_a)

def read_byte_then_close(s):
    data = s.recv(1)
    s.close()

t = threading.Thread(target=read_byte_then_close, args=(sock_b,))
t.start()

file_a = sock_a.makefile('w')
file_a.writelines(['a'*8192]*1000)
file_a.flush()
t.join()
"""

It's not quite good enough to add to the test suite yet IMO, but it's a starting point.

Chatting with Taggnostr on IRC I've trimmed that reproduction down to something much cleaner (no magic numbers or threads involved):

import socket
sock_a, sock_b = socket.socketpair()
sock_a = socket.socket(_sock=sock_a)
sock_b.close()
file_a = sock_a.makefile('w')
file_a.write('x')
file_a.flush()

Here is the patch.

Patch accepted, please apply for 2.6.6.

Done in r83964.