excel表格vba编程的方法步骤（excel vba编程基础知识）
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2022-05-30
Python编程：threading多线程
进程process：应用程序以一个整体的形式暴露给操作系统管理，里边包含对各种资源的调用，内存的分配，对各种资源管理的集合
线程thread：操作系统最小的调度单位，是一串指令的集合
进程 要操作cpu，必须先创建一个线程
进程与线程区别：线程共享，进程独立
线程共享内存空间，进程内存是独立的
同一个进程之间的线程可以直接通信，两个进程必须通过中间代理才能通信，创建新线程很简单，创建新进程需要对其父进程进行一次克隆
一个线程可以控制和操作统一进程里的其他线程，进程只能操作子进程
GIL：Global Interpreter Lock
直接调用
import threading import time def run(n): print("task:", n) time.sleep(2) t1 = threading.Thread(target=run, args=("t1",)) t2 = threading.Thread(target=run, args=("t2",)) t3 = threading.Thread(target=run, args=("t3",)) t1.start() t2.start() t3.start() """ task: t1 task: t2 task: t3 """
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继承式调用
import threading import time class MyThread(threading.Thread): def __init__(self, n, sleep_time): super(MyThread, self).__init__() self.n = n self.sleep_time = sleep_time def run(self): # 需要运行的代码 print("task:", self.n) time.sleep(self.sleep_time) print("task done", self.n, threading.current_thread(), threading.active_count()) t1 = MyThread("t1", 2) t2 = MyThread("t2", 3) t3 = MyThread("t3", 4) t1.start() t2.start() t3.start() # 等待线程执行完毕继续主线程，阻塞 t1.join() # wait() t2.join() t3.join() print("...main...", threading.current_thread(), threading.active_count()) # 主线程 """ task: t1 task: t2 task: t3 task done t1
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多线程调用
# 主线程与子线程是并行的 import threading import time def run(n): print("task:", n) time.sleep(2) print("task done", n) start_time = time.time() threads = [] # 保存线程列表 for i in range(5): t = threading.Thread(target=run, args=("t%s"%i,)) t.start() threads.append(t) # 将所有线程阻塞 for t in threads: t.join() end_time = time.time() print("time:", end_time - start_time) """ task: t0 task: t1 task: t2 task: t3 task: t4 task done t4 task done t2 task done t3 task done t1 task done t0 time: 2.0103650093078613 """
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守护线程
import threading import time def run(n): print("task:", n) time.sleep(2) print("task done", n) start_time = time.time() threads = [] # 保存线程列表 for i in range(5): t = threading.Thread(target=run, args=("t%s"%i,)) t.setDaemon(True) # 设置为守护线程，主线程停止随之停止 t.start() threads.append(t) time.sleep(2) # 等待部分线程执行完毕 end_time = time.time() print("time:", end_time - start_time) """ task: t0 task: t1 task: t2 task: t3 task: t4 task done t2 task done t4 task done t3 task done t1 task done t0 time: 2.0087130069732666 """
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互斥锁
import threading import time num = 0 lock = threading.Lock() # 实例化互斥锁 def run(n): global num lock.acquire() # 申请锁 time.sleep(2) num += 1 lock.release() # 释放锁 print(num) start_time = time.time() threads = [] # 保存线程列表 for i in range(5): t = threading.Thread(target=run, args=("t%s"%i,)) t.start() threads.append(t) for thread in threads: thread.join() # 等待部分线程执行完毕 end_time = time.time() print("time:", end_time - start_time) print("num:", num) """ 1 2 3 4 5 time: 10.027688980102539 num: 5 """
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递归锁
import threading import time num = 0 lock = threading.RLock() # 实例化递归锁,此处用普通互斥锁会卡死 def run1(): print("run1_start") lock.acquire() # 第二级锁 print("run1") lock.release() def run2(): lock.acquire() # 第二级锁 print("run2") lock.release() def run(): lock.acquire() # 第一级锁 print("run1_begin") run1() print("run2_begin") run2() print("run_end") lock.release() # 释放锁 start_time = time.time() t = threading.Thread(target=run) t.start() # t.join() # 等待全部线程执行完毕 while threading.active_count() > 1: print(threading.current_thread()) end_time = time.time() print("time:", end_time - start_time) """ run1_begin <_MainThread(MainThread, started 22552)> <_MainThread(MainThread, started 22552)> <_MainThread(MainThread, started 22552)> run1_start <_MainThread(MainThread, started 22552)> run1 run2_begin run2 run_end time: 0.0 """
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信号锁
import threading import time semaphore = threading.BoundedSemaphore(5) # 设置信号量，最多允许5个线程同时运行 def run(n): semaphore.acquire() # 信号锁 time.sleep(1) print("run", n) semaphore.release() start_time = time.time() for i in range(10): t = threading.Thread(target=run, args=(i,)) t.start() # 等待全部线程执行完毕 while threading.active_count() != 1: pass end_time = time.time() print("time:", end_time - start_time) """ run 1 run 2 run 4 run 0 run 3 run 5 run 7 run 8 run 9 run 6 time: 2.061771869659424 """
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Python 任务调度 多线程
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