1.多线程初体验

主线程的id和进程的id是一个
查看进程pid下有多少个线程

ps  -T -p pid

(base) D:\code\python_project\python_coroutine>C:/ProgramData/Anaconda3/python.exe d:/code/python_project/python_coroutine/01demo.py
threading.active_count=1
i am producer cnt=1 thread_id1 = 15984 thread_id2 = 15984
threading.active_count=2
i am consumer cnt=0 thread_id1 = 12828 thread_id2 = 12828
threading.active_count=3
i am producer cnt=1 thread_id1 = 15984 thread_id2 = 15984
i am consumer cnt=0 thread_id1 = 12828 thread_id2 = 12828
i am producer cnt=1 thread_id1 = 15984 thread_id2 = 15984

import threading
import time
cnt = 0
def producer():
    global cnt
    while True:
        cnt += 1
        print("i am producer cnt={} thread_id1 = {} thread_id2 = {}".format(cnt,threading.get_ident(), threading.get_native_id()))
        time.sleep(1) 
    pass
def consumer():
    global cnt
    while True:
        if cnt <= 0:
            continue
        cnt -= 1
        print("i am consumer cnt={} thread_id1 = {} thread_id2 = {}".format(cnt,threading.get_ident(), threading.get_native_id()))
        time.sleep(1)
if __name__ == "__main__":
    print("threading.active_count={}".format(threading.active_count()))
    t1 = threading.Thread(target=producer)
    t2 = threading.Thread(target=consumer)
    t1.start()
    print("threading.active_count={}".format(threading.active_count()))
    t2.start()
    print("threading.active_count={}".format(threading.active_count()))

查看当前程序的活跃线程数量

threading.active_count()

2.单线程下载器

下载模块：从网络上下载图片 I/O密集型
哈希模块：cpu密集
存储模块：I/O密集
单线程的是串行的，先下载，再哈希计算重命名，再存储，都是在主线程完成。
实际上三个功能应该并行起来：主线程负责调度，三个线程分别实现下载，哈希和存储。