python of concurrent programming (thread theory, two ways open threads, processes and threads difference, otherwise the thread object)

9.9 Theory Thread

1. What is the thread thread refers to an assembly line process work

The process is simply not an execution unit, the process is actually a resource unit, a native threads within a process, thread execution unit is

2, the process VS thread

• They threads within the same process share resources within the process, thread resources within the different processes must be isolated

• Creating threads is less expensive to process than create more

9.91 in two ways open thread

method one:

from multiprocessing Import Process
 from Threading Import the Thread
 Import Time 
DEF Task (name):
     Print ( ' % S running IS ' % name) 
    the time.sleep ( . 3) # end of the main thread running to wait for the end of the sub-thread, as further sub-thread to use the resources of the main thread 
IF the __name__ == ' __main__ ' : 
    T = the thread (target = Task, args = ( ' Egon ' ,))
     # T = Process (target = Task, args = ( 'Egon',))     t.start ()
     Print 
( " Main thread " ) # Egon main thread running IS

Second way:

from multiprocessing import Process
from threading import Thread
import time
​
class MyThread(Thread):
    def run(self):
        print('%s is running' %self.name)
        time.sleep(3)
​
if __name__ == '__main__':
    t=MyThread()
    t.start()
    print('主线程')#Thread-1 is running the main thread

9.92 difference between processes and threads

1、PID:

from threading import Thread
import time,os
​
def task():
    print('%s is running' %os.getpid())#11352 is running
    time.sleep(3)
​
if __name__ == '__main__':
    t=Thread(target=task,)
    t.start()
    print('主线程',os.getpid())#主线程 11352

2, thread creation overhead small

3, multiple threads share resources within the process in the same process

from threading import Thread
import time,os
​
x=1000
def task():
    global x
    x=0
​
if __name__ == '__main__':
    t=Thread(target=task,)
    t.start()
    t.join()
    print('主线程',x)  #主线程 0

Other methods 9.93 thread object

• is_alive (): Returns the thread is active

• getName (): Returns the thread name

• setName (): Set the thread name

• enumerate (): Returns a list of running threads. Refers to the thread starts running, before the end, it does not include a thread before starting and after termination.

• active_count (): Returns the number of running threads, and len (threading.enumerate ()) have the same result.

• current_thread (): Returns the current thread variable

from threading import Thread,current_thread,active_count,enumerate
import time,os
​
def task():
    print('%s is running' %current_thread().name)
    time.sleep(3)
​
if __name__ == '__main__':
    t1=Thread(target=task,name='第一个线程')#第一个线程 is running
    t2=Thread(target=task,)#Thread-1 is running
    t3=Thread(target=task,)#Thread-2 is running
    t1.start()
    t2.start()
    t3.start()
​
    print(t1.is_alive())#True
    print(active_count())#4
    print(enumerate())#[<_MainThread(MainThread, started 13004)>, <Thread(第一个线程, started 14044)>, <Thread(Thread-1, started 11380)>, <Thread(Thread-2, started 9452)>]
    print('主线程',current_thread().name)#主线程 MainThread