python-46-多线程

# 初识多线程：threading
from threading import Thread
import time
def func(i):
    time.sleep(2)
    print(i)

if __name__ == ‘__main__‘:
    for i in range(5):
        thread=Thread(target=func,args=(i,))
        thread.start()

# 2、类中多线程
from threading import Thread
import time
class MyTread(Thread):
    def __init__(self,i):
        super().__init__()
        self.i=i
    def run(self):          # 必须有run方法
        time.sleep(1)
        print(self.i)

for i in range(10):
    t=MyTread(i)
    t.start()

# 3、代码/数据/文件是共享的实例
from threading import Thread
import time
num=10                      # 定义一个全局变量
class MyTread(Thread):
    def __init__(self,i):
        super().__init__()
        self.i=i
    def run(self):          # 必须有run方法
        global num          # global声明变量
        time.sleep(1)
        print(‘线程：‘,self.i+num) # i+num
for i in range(10):
    t=MyTread(i)
    t.start()

# 4、多线程与多进程效率对比,同是100个。
from threading import Thread
import time
from multiprocessing import Process
def func(i):
    return i+i
if __name__ == ‘__main__‘:
    start=time.time()
    t_lst=[]
    for i in range(100):
        t=Thread(target=func,args=(i,))     # 多线程
        t.start()
        t_lst.append(t)
    for i in t_lst:i.join()
    t1=time.time()-start
    print(‘多线程执行时间：‘,t1)

    start=time.time()
    p_lst=[]
    for i in range(100):
        p=Process(target=func,args=(i,))    # 多进程
        p.start()
        t_lst.append(p)
    for i in p_lst:i.join()
    t2=time.time()-start
    print(‘多进程执行时间：‘,t2)

# threading模块其它方法
import threading,time
def func(i):
    time.sleep(0.5)
    print(i,threading.current_thread())     # 查看线程名字与id
    print(i,threading.get_ident())          # 查看线程id

for i in range(5):
    threading.Thread(target=func,args=(i,)).start()
print(threading.active_count())             # 查看活跃线程数(注意要加上主线程)
print(threading.enumerate())                # 查看线程所有项
print(threading.current_thread())           # 查看线程名字与id