I'm playing around with some threading stuff right now, and I'm having a
little trouble calling a function from one thread that affects another.
Here's my setup:
py> import os, threading, time
py> def write(file_in, input_lines):
.... for line in input_lines:
.... time.sleep(0.5)
.... file_in.write(l ine)
.... file_in.flush()
.... file_in.close()
....
py> def read(file_out, output_list):
.... while True:
.... line = file_out.readli ne()
.... if not line:
.... break
.... output_list.app end(line)
....
py> def runthreads(lst) :
.... file_in, file_out, file_err = os.popen3('cat' )
.... write_thread = threading.Threa d(
.... target=write, args=(file_in,
.... ['%s\n' % x for x in range(10)]))
.... read_thread = threading.Threa d(target=read,
.... args=(file_out, lst))
.... write_thread.st art()
.... read_thread.sta rt()
.... write_thread.jo in()
.... read_thread.joi n()
....
Basically, I start one thread to read and one thread to write (from a
os.pipe). This all works fine for me:
py> lst = []
py> runthreads(lst)
py> lst
['0\n', '1\n', '2\n', '3\n', '4\n', '5\n', '6\n', '7\n', '8\n', '9\n']
I run into a problem though when I try to call an update method every
time I read a line:
py> class updatinglist(li st):
.... def __init__(self, updater):
.... super(updatingl ist, self).__init__( )
.... self.updater = updater
.... def append(self, item):
.... super(updatingl ist, self).append(it em)
.... self.updater(le n(self))
....
py> def update(i):
.... print i
....
py> lst = updatinglist(up date)
py> runthreads(lst)
1
2
3
4
5
6
7
8
9
10
py> lst
['0\n', '1\n', '2\n', '3\n', '4\n', '5\n', '6\n', '7\n', '8\n', '9\n']
I get the correct output, but if you run this yourself, you'll see that
the numbers 1 through 10 aren't printed in sync with the writes (i.e.
every half second); they're all printed at the end. Could someone
explain to me why this happens, and how (if possible) I can get the
numbers printed in sync with the appends to the list?
Thanks,
Steve
little trouble calling a function from one thread that affects another.
Here's my setup:
py> import os, threading, time
py> def write(file_in, input_lines):
.... for line in input_lines:
.... time.sleep(0.5)
.... file_in.write(l ine)
.... file_in.flush()
.... file_in.close()
....
py> def read(file_out, output_list):
.... while True:
.... line = file_out.readli ne()
.... if not line:
.... break
.... output_list.app end(line)
....
py> def runthreads(lst) :
.... file_in, file_out, file_err = os.popen3('cat' )
.... write_thread = threading.Threa d(
.... target=write, args=(file_in,
.... ['%s\n' % x for x in range(10)]))
.... read_thread = threading.Threa d(target=read,
.... args=(file_out, lst))
.... write_thread.st art()
.... read_thread.sta rt()
.... write_thread.jo in()
.... read_thread.joi n()
....
Basically, I start one thread to read and one thread to write (from a
os.pipe). This all works fine for me:
py> lst = []
py> runthreads(lst)
py> lst
['0\n', '1\n', '2\n', '3\n', '4\n', '5\n', '6\n', '7\n', '8\n', '9\n']
I run into a problem though when I try to call an update method every
time I read a line:
py> class updatinglist(li st):
.... def __init__(self, updater):
.... super(updatingl ist, self).__init__( )
.... self.updater = updater
.... def append(self, item):
.... super(updatingl ist, self).append(it em)
.... self.updater(le n(self))
....
py> def update(i):
.... print i
....
py> lst = updatinglist(up date)
py> runthreads(lst)
1
2
3
4
5
6
7
8
9
10
py> lst
['0\n', '1\n', '2\n', '3\n', '4\n', '5\n', '6\n', '7\n', '8\n', '9\n']
I get the correct output, but if you run this yourself, you'll see that
the numbers 1 through 10 aren't printed in sync with the writes (i.e.
every half second); they're all printed at the end. Could someone
explain to me why this happens, and how (if possible) I can get the
numbers printed in sync with the appends to the list?
Thanks,
Steve
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