[Python-bugs-list] [ python-Bugs-685846 ] raw_input defers alarm signal

[SourceForge.net]

Bugs item #685846, was opened at 2003-02-13 10:11
You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=685846&group_id=5470

Category: Python Library
Group: Python 2.2
Status: Open
Resolution: None
Priority: 5
Submitted By: paul rubin (phr)
Assigned to: Nobody/Anonymous (nobody)
Summary: raw_input defers alarm signal

Initial Comment:
import signal
def handle(a,b):
   print "received signal"
signal.signal(signal.SIGALRM, handle)
signal.alarm(5)
name = raw_input('Please enter your name within 5
seconds: ')


waits for input forever instead of getting the signal
thrown
after 5 seconds.  If you wait more than 5 seconds before
typing your name, the signal does get handled after you
finally enter your input.

The workaround of calling sys.stdin.readline() instead of
raw_input does the right thing, so something is funny about
the raw_input function.


----------------------------------------------------------------------

Comment By: Michael Stone (mbrierst)
Date: 2003-03-19 17:51

Message:
Logged In: YES 
user_id=670441

This isn't just a readline problem,
it's consistent whether or not readline
is used.  Patch #706406 attempts
to fix this problem in a reasonable manner,
but it may not be possible to fix perfectly.
Signals always seem pretty hopeless to
get really right, and python hardly tries
most of the time.  (Only handling them in
the main thread...)

I think raw_input really doesn't WANT to
just give up when receiving a signal, so the
patch has it give up only when the signal
handler throws an exception.

----------------------------------------------------------------------

Comment By: Michael Hudson (mwh)
Date: 2003-02-13 11:46

Message:
Logged In: YES 
user_id=6656

I'm 99% sure this is readline's fault.

You might be able to test this by hiding the readline.so
from the interpreter.

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=685846&group_id=5470