py> import os, threading, time
py> def write(file_in, input_lines):
... for line in input_lines:
... time.sleep(0.5)
... file_in.write(line)
... file_in.flush()
... file_in.close()
...
py> def read(file_out, output_list):
... while True:
... line = file_out.readline()
... if not line:
... break
... output_list.append(line)
...
py> def runthreads(lst):
... file_in, file_out, file_err = os.popen3('cat')
... write_thread = threading.Thread(
... target=write, args=(file_in,
... ['%s\n' % x for x in range(10)]))
... read_thread = threading.Thread(target=read,
... args=(file_out, lst))
... write_thread.start()
... read_thread.start()
... write_thread.join()
... read_thread.join()
...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(list): ... def __init__(self, updater): ... super(updatinglist, self).__init__() ... self.updater = updater ... def append(self, item): ... super(updatinglist, self).append(item) ... self.updater(len(self)) ... py> def update(i): ... print i ... py> lst = updatinglist(update) 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 -- http://mail.python.org/mailman/listinfo/python-list
