python并发编程之线程实例解析

from queue import Queue
from threading import Thread
import random
import time
_sentinel = object()
def producer(out_q):
 n = 10
 while n:
 time.sleep(1)
 data = random.randint(0, 10)
 out_q.put(data)
 print("生产者生产了数据{0}".format(data))
 n -= 1
 out_q.put(_sentinel)
def consumer(in_q):
 while True:
 data = in_q.get()
 print("消费者消费了{0}".format(data))
 if data is _sentinel:
  in_q.put(_sentinel)
  break
q = Queue()
t1 = Thread(target=consumer, args=(q,))
t2 = Thread(target=producer, args=(q,))

t1.start()
t2.start()

from threading import Thread, Event
import time
def countdown(n, started_evt):
 print("countdown starting")
 # set将event的标识设置为True
 started_evt.set()
 while n > 0:
 print("T-mins", n)
 n -= 1
 time.sleep(2)

# 初始化的started_evt为False
started_evt = Event()
print("Launching countdown")
t = Thread(target=countdown, args=(10, started_evt,))
t.start()
# 会一直等待直到event的标志为True的时候
started_evt.wait()
print("countdown is running")

import threading
import time
class PeriodicTimer:
 """
 这里做了一个定时器
 """ def __init__(self, interval):
 self._interval = interval
 self._flag = 0
 self._cv = threading.Condition()

 def start(self):
 t = threading.Thread(target=self.run)
 t.daemon = True
 t.start()

 def run(self):
 while True:
  time.sleep(self._interval)
  with self._cv:
  # 这个点还是非常有意思的^=
  self._flag ^= 1
  self._cv.notify_all()

 def wait_for_tick(self):
 with self._cv:
  last_flag = self._flag

  while last_flag == self._flag:
  self._cv.wait()
# 下面两个分别为两个需要定时执行的任务
def countdown(nticks):
 while nticks > 0:
 ptimer.wait_for_tick()
 print('T-minus', nticks)
 nticks -= 1
def countup(last):
 n = 0
 while n < last:
 ptimer.wait_for_tick()
 print('Counting', n)
 n += 1
ptimer = PeriodicTimer(5)
ptimer.start()

threading.Thread(target=countdown, args=(10,)).start()
threading.Thread(target=countup, args=(5,)).start()

import threading
class SharedCounter:
 def __init__(self, initial_value=0):
 self._value = initial_value
 self._value_lock = threading.Lock()
 def incr(self,delta = 1):
 with self._value_lock:
  self._value += delta

 def decr(self, delta=1):
 with self._value_lock:
  self._value -= delta

import threading
class SharedCounter:
 _lock = threading.RLock()
 def __init__(self,initial_value=0):
 self._value = initial_value
 def incr(self,delta=1):
 with SharedCounter._lock:
  self._value += delta
 def decr(self,delta=1):
 with SharedCounter._lock:
  self.incr(-delta)

from threading import Semaphore
import requests
_fetch_url_sema = Semaphore(5)
def fetch_url(url):
 with _fetch_url_sema:
 return requests.get(url)

import threading
from contextlib import contextmanager

# 存储已经请求锁的信息
_local = threading.local()
@contextmanager
def acquire(*locks):
 # 把锁通过id进行排序
 locks = sorted(locks, key=lambda x: id(x))

 acquired = getattr(_local, 'acquired', [])

 if acquired and max(id(lock) for lock in acquired) >= id(locks[0]):
 raise RuntimeError("Lock order Violation")
 acquired.extend(locks)
 _local.acquired = acquired

 try:
 for lock in locks:
  lock.acquire()
 yield
 finally:
 for lock in reversed(locks):
  lock.release()
 del acquired[-len(locks):]
x_lock = threading.Lock()
y_lock = threading.Lock()
def thread_1():
 while True:
 with acquire(x_lock,y_lock):
  print("Thread-1")
def thread_2():
 while True:
 with acquire(y_lock,x_lock):
  print("Thread-2")
t1 = threading.Thread(target=thread_1)
t1.daemon = True
t1.start()

t2 = threading.Thread(target=thread_2)
t2.daemon = True
t2.start()