Python run()函数和start()函数的比较和差别

run() 方法并不启动一个新线程，就是在主线程中调用了一个普通函数而已。
start() 方法是启动一个子线程，线程名就是自己定义的name。
因此，如果你想启动多线程，就必须使用start()方法。

请看实例：（源代码）
1 使用run()方法启动线程，它打印的线程名是MainThread，也就是主线程。
import threading,time

def worker():
count = 1
while True:
if count >= 4:
break
time.sleep(1)
count += 1
print(“thread name = {}”.format(threading.current_thread().name))

print(“Start Test run()”)
t1 = threading.Thread(target=worker, name=“MyTryThread”)
t1.run()

print(“run() test end”)

运行结果：
Start Test run()
thread name = MainThread
thread name = MainThread
thread name = MainThread
run() test end
2 使用start()方法启动的线程名是我们定义线程对象时设置的name="MyThread"的值，如果没有设置name参数值，则会打印系统分配的Thread-1,Thread-2…这样的名称。

import threading,time

def worker():
count = 1
while True:
if count >= 4:
break
time.sleep(2)
count += 1
print(“thread name = {}”.format(threading.current_thread().name)) # 当前线程名

print(“Start Test start()”)
t = threading.Thread(target=worker, name=“MyTryThread”)
t.start()
t.join()

print(“start() test end”)
运行结果:
Start Test start()
thread name = MyTryThread
thread name = MyTryThread
thread name = MyTryThread
start() test end

3 两个子线程都用run()方法启动，但却是先运行t1.run()，运行完之后才按顺序运行t2.run()，两个线程都工作在主线程，没有启动新线程，thread ID都是一样的，因此，run()方法仅仅是普通函数调用。
import threading,time

def worker():
count = 1
while True:
if count >= 4:
break
time.sleep(2)
count += 1
print(“thread name = {}, thread id = {}”.format(threading.current_thread().name,
threading.current_thread().ident))

print(“Start Test run()”)
t1 = threading.Thread(target=worker, name=“t1”)
t2 = threading.Thread(target=worker, name=‘t2’)

t1.run()
t2.run()

print(“run() test end”)
运行结果:
Start Test run()
thread name = MainThread, thread id = 3920
thread name = MainThread, thread id = 3920
thread name = MainThread, thread id = 3920
thread name = MainThread, thread id = 3920
thread name = MainThread, thread id = 3920
thread name = MainThread, thread id = 3920
run() test end

4 使用start()方法启动了两个新的子线程并交替运行，每个子进程ID也不同。

import threading,time

def worker():
count = 1
while True:
if count >= 4:
break
time.sleep(2)
count += 1
print(“thread name = {}, thread id = {}”.format(threading.current_thread().name,
threading.current_thread().ident))

print(“Start Test start()”)
t1 = threading.Thread(target=worker, name=“MyTryThread1”)
t2 = threading.Thread(target=worker, name=“MyTryThread2”)
t1.start()
t2.start()
t1.join()
t2.join()
print(“start() test end”)

运行结果:
Start Test start()
thread name = MyTryThread1, thread id = 4628
thread name = MyTryThread2, thread id = 872
thread name = MyTryThread1, thread id = 4628
thread name = MyTryThread2, thread id = 872
thread name = MyTryThread1, thread id = 4628
thread name = MyTryThread2, thread id = 872
start() test end