I founded a nice package that is called kthread which simplify the threading in python. I have also found out that it is possible to name give a thread by its name etc:
import sys
import time
import kthread
def func():
try:
while True:
time.sleep(0.2)
finally:
sys.stdout.write("Greetings from Vice City!\n")
sys.stdout.flush()
t = kthread.KThread(target=func, name="KillableThread1")
t.start()
t.is_alive()
t.terminate()
t.is_alive()
Instead of doing t.terminate() I wonder if there is a possibility to remove a thread by given name?
The following piece of code might help.
thread_dict = {}
t1 = kthread.KThread(target=func, name="KillableThread1")
t2 = kthread.KThread(target=func, name="KillableThread2")
thread_dict[t1.name] = t1
thread_dict[t2.name] = t2
After that when you want to kill a thread then do the following:
thread_dict["KillableThread1"].terminate()
Related
The example I will describe here is purely conceptual so I'm not interested in solving this actual problem.
What I need to accomplish is to be able to asynchronously run a function based on a continuous output of a subprocess command, in this case, the windows ping yahoo.com -t command and based on the time value from the replies I want to trigger the startme function. Now inside this function, there will be some more processing done, including some database and/or network-related calls so basically I/O processing.
My best bet would be that I should use Threading but for some reason, I can't get this to work as intended. Here is what I have tried so far:
First of all I tried the old way of using Threads like this:
import subprocess
import re
import asyncio
import time
import threading
def startme(mytime: int):
print(f"Mytime {mytime} was started!")
time.sleep(mytime) ## including more long operation functions here such as database calls and even some time.sleep() - if possible
print(f"Mytime {mytime} finished!")
myproc = subprocess.Popen(['ping', 'yahoo.com', '-t'], shell=True, stdout=subprocess.PIPE)
def main():
while True:
output = myproc.stdout.readline()
if myproc.poll() is not None:
break
myoutput = output.strip().decode(encoding="UTF-8")
print(myoutput)
mytime = re.findall("(?<=time\=)(.*)(?=ms\s)", myoutput)
try:
mytime = int(mytime[0])
if mytime < 197:
# startme(int(mytime[0]))
p1 = threading.Thread(target=startme(mytime), daemon=True)
# p1 = threading.Thread(target=startme(mytime)) # tried with and without the daemon
p1.start()
# p1.join()
except:
pass
main()
But right after startme() fire for the first time, the pings stop showing and they are waiting for the startme.time.sleep() to finish.
I did manage to get this working using the concurrent.futures's ThreadPoolExecutor but when tried to replace the time.sleep() with the actual database query I found out that my startme() function will never complete so no Mytime xxx finished! message is ever shown nor any database entry is being made.
import sqlite3
import subprocess
import re
import asyncio
import time
# import threading
# import multiprocessing
from concurrent.futures import ThreadPoolExecutor
from concurrent.futures import ProcessPoolExecutor
conn = sqlite3.connect('test.db')
c = conn.cursor()
c.execute(
'''CREATE TABLE IF NOT EXISTS mytable (id INTEGER PRIMARY KEY, u1, u2, u3, u4)''')
def startme(mytime: int):
print(f"Mytime {mytime} was started!")
# time.sleep(mytime) ## including more long operation functions here such as database calls and even some time.sleep() - if possible
c.execute("INSERT INTO mytable VALUES (null, ?, ?, ?, ?)",(1,2,3,mytime))
conn.commit()
print(f"Mytime {mytime} finished!")
myproc = subprocess.Popen(['ping', 'yahoo.com', '-t'], shell=True, stdout=subprocess.PIPE)
def main():
while True:
output = myproc.stdout.readline()
myoutput = output.strip().decode(encoding="UTF-8")
print(myoutput)
mytime = re.findall("(?<=time\=)(.*)(?=ms\s)", myoutput)
try:
mytime = int(mytime[0])
if mytime < 197:
print(f"The time {mytime} is low enought to call startme()" )
executor = ThreadPoolExecutor()
# executor = ProcessPoolExecutor() # I did tried using process even if it's not a CPU-related issue
executor.submit(startme, mytime)
except:
pass
main()
I did try using asyncio but I soon realized this is not the case but I'm wondering if I should try aiosqlite
I also thought about using asyncio.create_subprocess_shell and run both as parallel subprocesses but can't think of a way to wait for a certain string from the ping command that would trigger the second script.
Please note that I don't really need a return from the startme() function and the ping command example is conceptually derived from the mitmproxy's mitmdump output command.
The first code wasn't working as I did a stupid mistake when creating the thread so p1 = threading.Thread(target=startme(mytime)) does not take the function with its arguments but separately like this p1 = threading.Thread(target=startme, args=(mytime,))
The reason why I could not get the SQL insert statement to work in my second code was this error:
SQLite objects created in a thread can only be used in that same thread. The object was created in thread id 10688 and this is thread id 17964
that I didn't saw until I wrapped my SQL statement into a try/except and captured the error. So I needed to make the SQL database connection inside my startme() function
The other asyncio stuff was just nonsense and cannot be applied to the current issue here.
I am writing a python library that will be used on unix/windows. I am facing an issue with terminating t1 thread. I have tried setting it to daemon thread but because the library is sometimes used in IDE/applications, t1 thread won't close until the whole application closes - which is not desired. Now, I am trying to change it to non-daemon thread and handle the termination manually.
def threadclick(id, stop):
while(True):
//do things repetitively //
if stop():
break
def main():
global stop_thread
stop_thread = False
port_string1 = port_string
t1 = threading.Thread(target=threadclick, args=(id, lambda : stop_thread))
t1.start()
I need to be able to close it by calling this function:
def close_thread():
global stop_thread
stop_thread = True
t1.join
of course it is giving me t1 is undefined error but I am not sure how to declare it globally.
Passig a constant value read from a simple scalar,
rather than passing a reference, is a concern,
as you wouldn't want to keep re-reading an unchanging value.
A dict will be convenient.
The function you were using seemed a little on the complex side.
Also, you'd probably be better off passing around a reference,
rather than relying on a global.
Use this:
def threadclick(id, status):
while not status['stop']:
do_things()
status = dict(stop=False)
def main():
status['stop'] = False
t1 = threading.Thread(target=threadclick, args=(id, status))
t1.start()
wait_for_things_to_happen()
close_thread(t1, status)
def close_thread(t1, status):
status['stop'] = True
t1.join()
I have a simple twisted TCP server running absolutely fine, it basically deals with database requests and displays the right things its just an echo client with a bunch of functions, the database that is being read also updates I have this refresh function to open the database and refresh it however if I add this to the message functions it'll take too long to respond as the refresh function takes around 6/7 seconds to complete, my initial idea was to have this function in a while loop and running constantly refreshing every 5/10 mins but after reading about the global interpreter lock its made me think that that isn't possible, any suggestions on how to run this function in the background of my code would be greatly appreciated
I've tried having it in a thread but it doesn't seem to run at all when I start the thread, I put it under the if name == 'main': function and no luck!
Here is my refresh function
def refreshit()
Application = win32com.client.Dispatch("Excel.Application")
Workbook = Application.Workbooks.open(database)
Workbook.RefreshAll()
Workbook.Save()
Application.Quit()
xlsx = pd.ExcelFile(database)
global datess
global refss
df = pd.read_excel(xlsx, sheet_name='Sheet1')
datess = df.groupby('documentDate')
refss = df.groupby('reference')
class Echo(Protocol):
global Picked_DFS
Picked_DFS = None
label = None
global errors
global picked
errors = []
picked = []
def dataReceived(self, data):
"""
As soon as any data is received, write it back.
"""
response = self.handle_message(data)
print('responding with this')
print(response)
self.transport.write(response)
def main():
f = Factory()
f.protocol = Echo
reactor.listenTCP(8000, f)
reactor.run()
if __name__ == '__main__':
main()
I had tried this to no avail
if __name__ == '__main__':
main()
thread = Thread(target = refreshit())
thread.start()
thread.join()
You have an important error on this line:
thread = Thread(target = refreshit())
Though you have not included the definition of refreshit (perhaps a function to consider renaming), I assume refreshit is a function that performs your refresh.
In this case, what you are doing here is calling refreshit and waiting for it to return a value. Then, the value it returns is used as the target of the Thread you create here. This is probably not what you meant. Instead:
thread = Thread(target = refreshit)
That is, refreshit itself is what you want the target of the thread to be.
You also need to be sure to sequence your operations so that everything gets to run concurrently:
if __name__ == '__main__':
# Start your worker/background thread.
thread = Thread(target = refreshit)
thread.start()
# Run Twisted
main()
# Cleanup/wait on your worker/background thread.
thread.join()
You may also just want to use Twisted's thread support instead of using the threading module directly (but this is not mandatory).
if __name__ == '__main__':
# Start your worker/background thread.
thread = Thread(target = refreshit)
thread.start()
# Run Twisted
main()
# Cleanup/wait on your worker/background thread.
thread.join()
That's my code:
import threading
import queue
qq=queue.Queue(10)
def x11grab(n):
print('haha')
while True:
a='abcd'+str(n)
n+=1
qq.put(a)
print('put queue:',a)
def rtpsend():
while True:
s=qq.get()
head=s[:4]
body=s[4:]
print('head',head)
print('body',body)
t1=threading.Thread(target=x11grab,args=(1,))
t2=threading.Thread(target=rtpsend)
t1.start
t2.start
I wanna x11grab() function put string 'abcd1','abcd2'... into queue,and rtpsend() function get the string from queue, and display it. It's a demo, but it didn't work. I think your advice could be helpful.:-)
You never start your threads! change
t1.start
t2.start
to
t1.start()
t2.start()
I'm using a thread to read Strings from a stream (/dev/tty1) while processing other things in the main loop. I would like the Thread to terminate together with the main program when pressing CTRL-C.
from threading import Thread
class myReader(Thread):
def run(self):
with open('/dev/tty1', encoding='ascii') as myStream:
for myString in myStream:
print(myString)
def quit(self):
pass # stop reading, close stream, terminate the thread
myReader = Reader()
myReader.start()
while(True):
try:
pass # do lots of stuff
KeyboardInterrupt:
myReader.quit()
raise
The usual solution - a boolean variable inside the run() loop - doesn't work here. What's the recommended way to deal with this?
I can just set the Daemon flag, but then I won't be able to use a quit() method which might prove valuable later (to do some clean-up). Any ideas?
AFAIK, there is no built-in mechanism for that in Python 3 (just as in Python 2). Have you tried the proven Python 2 approach with PyThreadState_SetAsyncExc, documented here and here, or the alternative tracing approach here?
Here's a slightly modified version of the PyThreadState_SetAsyncExc approach from above:
import threading
import inspect
import ctypes
def _async_raise(tid, exctype):
"""raises the exception, performs cleanup if needed"""
if not inspect.isclass(exctype):
exctype = type(exctype)
res = ctypes.pythonapi.PyThreadState_SetAsyncExc(ctypes.c_long(tid), ctypes.py_object(exctype))
if res == 0:
raise ValueError("invalid thread id")
elif res != 1:
# """if it returns a number greater than one, you're in trouble,
# and you should call it again with exc=NULL to revert the effect"""
ctypes.pythonapi.PyThreadState_SetAsyncExc(tid, None)
raise SystemError("PyThreadState_SetAsyncExc failed")
def stop_thread(thread):
_async_raise(thread.ident, SystemExit)
Make your thread a daemon thread. When all non-daemon threads have exited, the program exits. So when Ctrl-C is passed to your program and the main thread exits, there's no need to explicitly kill the reader.
myReader = Reader()
myReader.daemon = True
myReader.start()