Python - Timer Threads

標籤：

 

A Timer starts its work after a delay and can be canceled at any point within that delay time period.

 

Threading

 

Python includes sophisticated tools for managing concurrent operations using processes and threads. Even many relatively simple programs can be made to run faster by applying techniques for running parts of the job concurrently using these modules.

subprocess provides an API for creating and communicating with secondary processes. It is especially good for running programs that produce or consume text, since the API supports passing data back and forth through the standard input and output channels of the new process.

The signal module exposes the UNIX signal mechanism for sending events to other processes. The signals are processed asynchronously, usually by interrupting what the program is doing when the signal arrives. Signalling is useful as a coarse messaging system, but other inter-process communication techniques are more reliable and can deliver more complicated messages.

threading includes a high-level, object-oriented API for working with concurrency from Python. Thread objects run concurrently within the same process and share memory. Using threads is an easy way to scale for tasks that are more I/O bound than CPU bound.

The multiprocessing module mirrors threading, except that instead of a Thread class it provides a Process. Each Process is a true system process without shared memory, but multiprocessing provides features for sharing data and passing messages between them. In many cases, converting from threads to processes is as simple as changing a few import statements.

 

import threadingimport timeimport logginglogging.basicConfig(level=logging.DEBUG,    format=‘(%(threadName)-10s) %(message)s‘,)def worker():    while 1:        time.sleep(3)        logging.debug(‘worker running‘)threads = []for i in range(2):        # t = threading.Thread(target=worker)    t = threading.Timer(1, worker)    threads.append(t)    t.start()    logging.debug(‘loop running‘)

 

將threading.Thread對象改為Timer,構造對象的參數也改為相應的(延遲時間, 函數名).

比較重要的是綠色背景的代碼,這個是用於調試。這也提醒了我,線程是進程的一個“邏輯”分支。

調試資訊如下:

(MainThread) loop running(MainThread) loop running(Thread-2  ) worker running(Thread-1  ) worker running(Thread-1  ) worker running(Thread-2  ) worker running(Thread-2  ) worker running(Thread-1  ) worker running(Thread-1  ) worker running(Thread-2  ) worker running

　　

以下是我自己用畫圖的理解:

 

Python - Timer Threads