class Thread(_Verbose):
    """A class that represents a thread of control.

    This class can be safely subclassed in a limited fashion.

    """
    __initialized = False
    # Need to store a reference to sys.exc_info for printing
    # out exceptions when a thread tries to use a global var. during interp.
    # shutdown and thus raises an exception about trying to perform some
    # operation on/with a NoneType
    __exc_info = _sys.exc_info
    # Keep sys.exc_clear too to clear the exception just before
    # allowing .join() to return.
    __exc_clear = _sys.exc_clear

    def __init__(self, group=None, target=None, name=None,
                 args=(), kwargs=None, verbose=None):
        """This constructor should always be called with keyword arguments. Arguments are:

        *group* should be None; reserved for future extension when a ThreadGroup
        class is implemented.

        *target* is the callable object to be invoked by the run()
        method. Defaults to None, meaning nothing is called.

        *name* is the thread name. By default, a unique name is constructed of
        the form "Thread-N" where N is a small decimal number.

        *args* is the argument tuple for the target invocation. Defaults to ().

        *kwargs* is a dictionary of keyword arguments for the target
        invocation. Defaults to {}.

        If a subclass overrides the constructor, it must make sure to invoke
        the base class constructor (Thread.__init__()) before doing anything
        else to the thread.

"""
        assert group is None, "group argument must be None for now"
        _Verbose.__init__(self, verbose)
        if kwargs is None:
            kwargs = {}
        self.__target = target
        self.__name = str(name or _newname())
        self.__args = args
        self.__kwargs = kwargs
        self.__daemonic = self._set_daemon()
        self.__ident = None
        self.__started = Event()
        self.__stopped = False
        self.__block = Condition(Lock())
        self.__initialized = True
        # sys.stderr is not stored in the class like
        # sys.exc_info since it can be changed between instances
        self.__stderr = _sys.stderr
……

#!/usr/bin/env python
# _*_ coding:utf-8 _*_
__Author__ = ‘KongZhaGen‘
import threading
import time

# 定义用于线程执行的函数
def sayhi(num):
    print "runing on number :%s"%num
    time.sleep(3)
    print ‘done‘,num

# main函数同时执行5个线程
def main():
    for i in range(5):
        t = threading.Thread(target=sayhi,args=(i,))
        t.start()

# 定义一个线程m，执行main函数
m = threading.Thread(target=main,args=())
# m线程定义为守护线程
m.setDaemon(True)
m.start()
# 守护线程执行结束，其中的所有子线程全部被迫结束运行，接着继续执行其后的代码
m.join()
print "---------main thread done-----"