ValueError: filedescriptor out of range in select()

Jean-Paul Calderone exarkun at
Tue Mar 17 15:45:19 CET 2009

On Tue, 17 Mar 2009 15:04:22 +0100, Laszlo Nagy <gandalf at> wrote:
>This is a long running process, written in Python. Only standard lib is 
>used. This process accepts connections on TCP sockets, read/write data.
>After about one day, it starts throwing this when I try to connect:
> [snip]
>  File "/usr/local/www/vhosts/", line 
>344, in read_data
>    ready =[fd], [], [], 0.2)
>ValueError: filedescriptor out of range in select()

For whatever reason, you're ending up with a lot of open files and/or sockets
(and/or any other resource based on file descriptors).  That results in new
file descriptors having large values (>=1024).

You cannot use select() with such file descriptors.  Try poll() instead,
or Twisted. ;)

However, the use of select() you demonstrated is an unusual one, and not
very good.  It looks like the only purpose is to work around a bug in
CPython on Windows where a process in a blocking read cannot be interrupted
by C-c in the console?  If that's the case, there may be other approaches
to solving the problem (like fixing the bug in CPython which causes this).


More information about the Python-list mailing list