Curses programming, threads?

Bartlomiej Rymarski <ba**@oceanic.wsisiz.edu.pl> wrote:

[...]
And the loader() function would run in a loop until connect_db() is
is finished. Is that possible in python? Or are there any other,
better ways to do it?
[...]

Oh, I forgot - I'm using Linux, and curses module in Python 2.3.

--
Bartek Rymarski <ba**@wsisiz.edu.pl>
$ %blow
bash: fg: %blow: no such job

Bartlomiej Rymarski <ba**@oceanic.wsisiz.edu.pl> wrote:

[...]
And the loader() function would run in a loop until connect_db() is
is finished. Is that possible in python? Or are there any other,
better ways to do it?
[...]

Oh, I forgot - I'm using Linux, and curses module in Python 2.3.

--
Bartek Rymarski <ba**@wsisiz.edu.pl>
$ %blow
bash: fg: %blow: no such job

Bartlomiej Rymarski <ba**@oceanic.wsisiz.edu.pl> wrote in message news:<co**********@portraits.wsisiz.edu.pl>...

Bartlomiej Rymarski <ba**@oceanic.wsisiz.edu.pl> wrote:

[...]
And the loader() function would run in a loop until connect_db() is
is finished. Is that possible in python? Or are there any other,
better ways to do it?
[...]

Oh, I forgot - I'm using Linux, and curses module in Python 2.3.

You don't need curses. Some time ago somebody (I forgot the name)
posted this spinner class:

class Spinner( threading.Thread ): # a google search should find the author

DELAY = 0.1
DISPLAY = [ '|', '/', '-', '\\' ]

def __init__( self, before='', after='' ):
threading.Thread.__init__( self )
self.before = before
self.after = after

def run( self ):
write, flush = sys.stdout.write, sys.stdout.flush
self.running = 1
pos = -1
while self.running:
pos = (pos + 1) % len(self.DISPLAY)
msg = self.before + self.DISPLAY[pos] + self.after
write( msg )
flush()
write( '\x08' * len(msg) )
time.sleep( self.DELAY )
write( ' ' * len(msg) + '\x08' * len(msg) )
flush()

def stop( self ):
self.running = 0
self.join()

if __name__=="__main__":
spinner = Spinner('Be patient please ...')
spinner.start()
time.sleep(5) # doing a long operation
spinner.stop()

Michele Simionato

Bartlomiej Rymarski <ba**@oceanic.wsisiz.edu.pl> wrote in message news:<co**********@portraits.wsisiz.edu.pl>...

Hello,

I'm writing this little program, and I've came across a function
that I need to call. Since the execution of the function takes a
real long time I want to put a timer, or an animated 'loading'
screen (it would be best if it was a progressbar). The questions is
how to make two commands to run at the same time.
[snip]
It would be best if I could operate with like this:

#v+
def function:
do loader() while
connect_db()
#v-

And the loader() function would run in a loop until connect_db() is
is finished. Is that possible in python?

Generally speaking, to do this in C, on Unix, without threads, one
would use the setitimer system call, along with SIGALARM. (Doubtful
available on all Unices, and there are probably other ways, but I'd
guess this is the most common way to do it. It is available on Linux;
I've used it before.) AFAIK, Python does not expose the setitimer
call, so you can't do it that way in Python without writing a C
extension. (It would be a pretty simple extension to write, though.)

In Python, you could use the signal.alarm() call in much the same way.
The downside is that you can only update the little animation once
per second. Something like this could do what you want (untested):

def alarm_handler(*args):
if loaded:
return
update_animation()
signal.alarm(1)

signal.signal(signal.SIGALARM,alarm_handler)
signal.alarm(1)
loaded = False
connect_db()
loaded = True

But I recommend threads for this. It's one of the easiest possible
uses of threads. There's no complex communication involved; locks and
semaphores and stuff aren't required. Just connect to the database in
a subthread, and have it set a global flag just before it exits.
Animate in a loop in the main thread, checking the flag every
iteration, and when it's true, you're done.
--
CARL BANKS

Michele Simionato <mi***************@gmail.com> wrote:

You don't need curses. Some time ago somebody (I forgot the name)
posted this spinner class:

class Spinner( threading.Thread ): # a google search should find the author
[...]

Great, thanks a lot.

--
Bartek Rymarski <ba**@wsisiz.edu.pl>
$ %blow
bash: fg: %blow: no such job

Carl Banks <im*****@aerojockey.com> wrote:

(...)
But I recommend threads for this. It's one of the easiest possible
uses of threads. There's no complex communication involved; locks and
semaphores and stuff aren't required. Just connect to the database in
a subthread, and have it set a global flag just before it exits.
Animate in a loop in the main thread, checking the flag every
iteration, and when it's true, you're done.
(...)

I'll try to do this with threads then. Thanks for the answer.

--
Bartek Rymarski <ba**@wsisiz.edu.pl>
$ %blow
bash: fg: %blow: no such job