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Python Tutorial
How to define and call threads in Python through the threading module
How to define and call threads in Python through the threading module
Define thread
The simplest method: use target to specify the target function to be executed by the thread, and then use start() to start it.
Grammar:
class threading.Thread(group=None, target=None, name=None, args=(), kwargs={})
group is always None and is reserved for future use. target is the name of the function to be executed. name is the thread name, the default is Thread-N, usually the default can be used. However, when the server-side program thread functions are different, it is recommended to name them.
#!/usr/bin/env python3
# coding=utf-8
import threading
def function(i):
print ("function called by thread {0}".format(i))
threads = []
for i in range(5):
t = threading.Thread(target=function , args=(i,))
threads.append(t)
t.start()
t.join()
Execution result:
$ ./threading_define.py
function called by thread 0 function called by thread 1 function called by thread 2 function called by thread 3 function called by thread 4
Determine the current thread
#!/usr/bin/env python3
# coding=utf-8
import threading
import time
def first_function():
print (threading.currentThread().getName()+ str(' is Starting \n'))
time.sleep(3)
print (threading.currentThread().getName()+ str( ' is Exiting \n'))
def second_function():
print (threading.currentThread().getName()+ str(' is Starting \n'))
time.sleep(2)
print (threading.currentThread().getName()+ str( ' is Exiting \n'))
def third_function():
print (threading.currentThread().getName()+\
str(' is Starting \n'))
time.sleep(1)
print (threading.currentThread().getName()+ str( ' is Exiting \n'))
if __name__ == "__main__":
t1 = threading.Thread(name='first_function', target=first_function)
t2 = threading.Thread(name='second_function', target=second_function)
t3 = threading.Thread(name='third_function',target=third_function)
t1.start()
t2.start()
t3.start()
Execution result:
$ ./threading_name.py
first_function is Starting second_function is Starting third_function is Starting third_function is Exiting second_function is Exiting first_function is Exiting
Use with logging module:
#!/usr/bin/env python3
# coding=utf-8
import logging
import threading
import time
logging.basicConfig(
level=logging.DEBUG,
format='[%(levelname)s] (%(threadName)-10s) %(message)s',
)
def worker():
logging.debug('Starting')
time.sleep(2)
logging.debug('Exiting')
def my_service():
logging.debug('Starting')
time.sleep(3)
logging.debug('Exiting')
t = threading.Thread(name='my_service', target=my_service)
w = threading.Thread(name='worker', target=worker)
w2 = threading.Thread(target=worker) # use default name
w.start()
w2.start()
t.start()
Execution result:
$ ./threading_names_log.py[DEBUG] (worker ) Starting
[DEBUG] (Thread-1 ) Starting [DEBUG] (my_service) Starting [DEBUG] (worker ) Exiting [DEBUG] (Thread-1 ) Exiting [DEBUG] (my_service) Exiting
Use threads in subclasses
Our previous threads were all created in the form of structured programming. Threads can also be created by integrating the threading.Thread class. The Thread class first completes some basic initialization and then calls its run(). The run() method will call the target function passed to the constructor.
#!/usr/bin/env python3
# coding=utf-8
import logging
import threading
import time
exitFlag = 0
class myThread (threading.Thread):
def __init__(self, threadID, name, counter):
threading.Thread.__init__(self)
self.threadID = threadID
self.name = name
self.counter = counter
def run(self):
print ("Starting " + self.name)
print_time(self.name, self.counter, 5)
print ("Exiting " + self.name)
def print_time(threadName, delay, counter):
while counter:
if exitFlag:
thread.exit()
time.sleep(delay)
print ("%s: %s" %(threadName, time.ctime(time.time())))
counter -= 1
# Create new threads
thread1 = myThread(1, "Thread-1", 1)
thread2 = myThread(2, "Thread-2", 2)
# Start new Threads
thread1.start()
thread2.start()
print ("Exiting Main Thread")
Execution result:
$ ./threading_subclass.py
Starting Thread-1 Starting Thread-2 Exiting Main Thread Thread-1: Tue Sep 15 11:03:21 2015 Thread-2: Tue Sep 15 11:03:22 2015 Thread-1: Tue Sep 15 11:03:22 2015 Thread-1: Tue Sep 15 11:03:23 2015 Thread-2: Tue Sep 15 11:03:24 2015 Thread-1: Tue Sep 15 11:03:24 2015 Thread-1: Tue Sep 15 11:03:25 2015 Exiting Thread-1 Thread-2: Tue Sep 15 11:03:26 2015 Thread-2: Tue Sep 15 11:03:28 2015 Thread-2: Tue Sep 15 11:03:30 2015 Exiting Thread-2
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