multithreading - identifying threads

Python Multithread

While each Thread instance has a name with a default value that can be changed as the thread is created. Naming threads is useful in server processes with multiple service threads handling different operations.

import threading
import time

def f1():
    print threading.currentThread().getName(), 'Starting'
    time.sleep(1)
    print threading.currentThread().getName(), 'Exiting'

def f2():
    print threading.currentThread().getName(), 'Starting'
    time.sleep(2)
    print threading.currentThread().getName(), 'Exiting'

def f3():
    print threading.currentThread().getName(), 'Starting'
    time.sleep(3)
    print threading.currentThread().getName(), 'Exiting'

t1 = threading.Thread(target=f1) # use default name
t2 = threading.Thread(name='f2', target=f2)
t3 = threading.Thread(name='f3', target=f3)

t1.start()
t2.start()
t3.start()

Output:

Thread-1 Starting
f2 Starting
f3 Starting
Thread-1 Exiting
f2 Exiting
f3 Exiting

Now the t2 and t3 threads have their names while t1 has a default name.

We were able to identify which thread is which by printing out the names of the threads, however, what we really need is the support from a logging module which will embed the thread name in every log message using the formatter code %(threadName)s. Including thread names in log messages makes it easier to trace those messages back to their source. Note that logging is thread-safe, so messages from different threads are kept distinct in the output.

import threading
import time
import logging

logging.basicConfig(level=logging.DEBUG,
                      format='[%(levelname)s] (%(threadName)-9s) %(message)s',)

def f1():
    logging.debug('Starting')
    time.sleep(1)
    logging.debug('Exiting')

def f2():
    logging.debug('Starting')
    time.sleep(2)
    logging.debug('Exiting')

def f3():
    logging.debug('Starting')
    time.sleep(3)
    logging.debug('Exiting')

t1 = threading.Thread(target=f1) # use default name
t2 = threading.Thread(name='f2', target=f2)
t3 = threading.Thread(name='f3', target=f3)

t1.start()
t2.start()
t3.start()

Output:

[DEBUG] (Thread-1 ) Starting
[DEBUG] (f2       ) Starting
[DEBUG] (f3       ) Starting
[DEBUG] (Thread-1 ) Exiting
[DEBUG] (f2       ) Exiting
[DEBUG] (f3       ) Exiting

The following keyword arguments are supported (from here):

Python Multithread