结论:启动线程,如果对target进行赋值,并且没有重写run方法,则线程start的时候会直接调用target中对应的方法
具体代码如下:
1、初始化一个线程
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threading.Thread.__init__( self ,target = thread_run()) def __init__( self , group = None , target = None , name = None , args = (), kwargs = None , * , daemon = None ): assert group is None , "group argument must be None for now" if kwargs is None : kwargs = {} self ._target = target self ._name = str (name or _newname()) self ._args = args self ._kwargs = kwargs |
2、调用start启动线程
最终调用_start_new_thread方法,self._bootstrap作为传参
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thread1.start() def start( self ): if not self ._initialized: raise RuntimeError( "thread.__init__() not called" ) if self ._started.is_set(): raise RuntimeError( "threads can only be started once" ) with _active_limbo_lock: _limbo[ self ] = self try : _start_new_thread( self ._bootstrap, ()) except Exception: with _active_limbo_lock: del _limbo[ self ] raise self ._started.wait() |
3、_start_new_thread等同于启动一个新线程,并在新线程中调用回调函数
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_start_new_thread = _thread.start_new_thread def start_new_thread(function: Callable [..., Any ], args: tuple [ Any , ...], kwargs: dict [ str , Any ] = ...) - > int : ... |
4、执行的回调函数就是上文传入的self._bootstrap, _bootstrap方法直接调用_bootstrap_inner(),而bootstrap_inner则调用run方法
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def _bootstrap_inner( self ): try : self ._set_ident() self ._set_tstate_lock() if _HAVE_THREAD_NATIVE_ID: self ._set_native_id() self ._started. set () with _active_limbo_lock: _active[ self ._ident] = self del _limbo[ self ] if _trace_hook: _sys.settrace(_trace_hook) if _profile_hook: _sys.setprofile(_profile_hook) try : self .run() |
5、最终调用run方法
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def run( self ): try : if self ._target: self ._target( * self ._args, * * self ._kwargs) finally : # Avoid a refcycle if the thread is running a function with # an argument that has a member that points to the thread. del self ._target, self ._args, self ._kwargs |
结论:
如果run方法被重写,则直接调用重写的run方法
如果run方法没有被重写,并且target被定义,则会直接调用线程创建时候的target方法,否则什么也不做
此处遇到一问题:
指定target参数,在执行过程中,打印的进程名mainthread(主进程),而不是之前所赋的进程名
threading.Thread.init(self,target=thread_run())
分析后发现赋予target的是执行的函数体,因此会先执行thread_run函数,执行结束后,将thread_run的返回值赋给了target,因为thread_run没有返回值,因此target的值是None,如果此时没有重写run函数,那么线程什么都不会做。 thread_run的执行是在主线程,而不是我们所认为的在子线程中执行thread_run
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def thread_run(): print ( "overwrite: 开始线程:" + threading.current_thread().name) time.sleep( 2 ) print ( "overwrite: 退出线程:" + threading.current_thread().name) class myThread (threading.Thread): def __init__( self , threadID, name, delay): threading.Thread.__init__( self ,target = thread_run()) self .threadID = threadID self .name = name self .delay = delay thread1.start() thread1.join() print ( "退出主线程" ) |
运行结果:
overwrite: 开始线程:MainThread
overwrite: 退出线程:MainThread
退出主线程
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原文链接:https://blog.csdn.net/u011087238/article/details/122896458