import queue
import threading
class ThreadPool(object):
  def __init__(self, max_num=20):
    self.queue = queue.Queue(max_num) #创建队列，最大数为20
    for i in range(max_num):
      self.queue.put(threading.Thread) #将类名放入队列中
  def get_thread(self):
    return self.queue.get() #从队列中取出类名
  def add_thread(self):
    self.queue.put(threading.Thread) #进类名放入队列中
def func(arg, p): #定义一个函数
  print(arg)
  import time
  time.sleep(2)
  p.add_thread()
pool = ThreadPool(10) #创建对象，并执行该类的构造方法，即将线程的类名放入队列中
for i in range(30):
  thread = pool.get_thread() #调用该对象的get_thread方法，取出类名
  t = thread(target=func, args=(i, pool)) #创建对象，执行func，参数在args中
  t.start()

import queue
import threading
import contextlib
import time
StopEvent = object()
class ThreadPool(object):
  def __init__(self, max_num, max_task_num = None):
    if max_task_num:
      self.q = queue.Queue(max_task_num)
    else:
      self.q = queue.Queue()
    self.max_num = max_num
    self.cancel = False
    self.terminal = False
    self.generate_list = []
    self.free_list = []
  def run(self, func, args, callback=None):
    """
    线程池执行一个任务
    :param func: 任务函数
    :param args: 任务函数所需参数
    :param callback: 任务执行失败或成功后执行的回调函数，回调函数有两个参数1、任务函数执行状态；2、任务函数返回值（默认为None，即：不执行回调函数）
    :return: 如果线程池已经终止，则返回True否则None
    """
    if self.cancel:
      return
    if len(self.free_list) == 0 and len(self.generate_list) < self.max_num:
      self.generate_thread()
    w = (func, args, callback,)
    self.q.put(w)
  def generate_thread(self):
    """
    创建一个线程
    """
    t = threading.Thread(target=self.call)
    t.start()
  def call(self):
    """
    循环去获取任务函数并执行任务函数
    """
    current_thread = threading.currentThread()
    self.generate_list.append(current_thread)
    event = self.q.get()
    while event != StopEvent:
      func, args, callback = event
      try:
        result = func(*args)
        success = True
      except Exception as e:
        success = False
        result = None
      if callback is not None:
        try:
          callback(success, result)
        except Exception as e:
          pass
      with self.worker_state(self.free_list, current_thread):
        if self.terminal:
          event = StopEvent
        else:
          event = self.q.get()
    else:
      self.generate_list.remove(current_thread)
  def close(self):
    """
    执行完所有的任务后，所有线程停止
    """
    self.cancel = True
    count = len(self.generate_list)
    while count:
      self.q.put(StopEvent)
      count -= 1
  def terminate(self):
    """
    无论是否还有任务，终止线程
    """
    self.terminal = True
    while self.generate_list:
      self.q.put(StopEvent)
    self.q.queue.clear()
  @contextlib.contextmanager
  def worker_state(self, state_list, worker_thread):
    """
    用于记录线程中正在等待的线程数
    """
    state_list.append(worker_thread)
    try:
      yield
    finally:
      state_list.remove(worker_thread)
# How to use
pool = ThreadPool(5)
def callback(status, result):
  # status, execute action status
  # result, execute action return value
  pass
def action(i):
  print(i)
for i in range(30):
  ret = pool.run(action, (i,), callback)
time.sleep(3)
print(len(pool.generate_list), len(pool.free_list))
print(len(pool.generate_list), len(pool.free_list))
pool.close()
# pool.terminate()