python学习 day14 进程和线程

Posted 2020-11-21 afly

 进程

# *********通过process创建单个进程
from multiprocessing import Process
import os

# 子进程要执行的代码
def run_proc(name):
    print(‘Run child process %s (%s)...‘ % (name, os.getpid()))     # 获取当前进程的名字,pid值

if __name__==‘__main__‘:
    print(‘Parent process %s.‘ %  os.getpid())
    p = Process(target=run_proc, args=(‘test‘,))    # 传入子进程的函数名,给子进程起个名字
    print(‘Child process will start.‘)
    p.start()
    p.join()
    print(‘Child process end.‘)

# Parent process 9976.
# Child process will start.
# Run child process test (9368)...
# Child process end.

# *************通过Pool创建多个进程,Pool内的参数为最多同时执行的进程数
from multiprocessing import Pool
import os, time, random

def long_time_task(name):
    print(‘Run task %s (%s)...‘ % (name, os.getpid()))
    start = time.time()
    time.sleep(random.random() * 3)
    end = time.time()
    print(‘Task %s runs %0.2f seconds.‘ % (name, (end - start)))

if __name__==‘__main__‘:
    print(‘Parent process %s.‘ % os.getpid())
    p = Pool(4)
    for i in range(5):
        p.apply_async(long_time_task, args=(i,))
    print(‘Waiting for all subprocesses done...‘)
    p.close()
    p.join()
    print(‘All subprocesses done.‘)

# Parent process 8808.
# Waiting for all subprocesses done...
# Run task 0 (2956)...
# Run task 1 (5296)...
# Run task 2 (8432)...
# Run task 3 (8412)...
# Task 3 runs 0.10 seconds.
# Run task 4 (8412)...
# Task 2 runs 0.41 seconds.
# Task 4 runs 1.61 seconds.
# Task 1 runs 1.90 seconds.
# Task 0 runs 2.09 seconds.
# All subprocesses done.



#****************** subprocess可以让我们方便的启动一个子进程,然后控制其输入和输出,nslookup是终端下的一个命令,能查到指定网址的ip
import subprocess

print(‘$ nslookup www.python.org‘)
r = subprocess.call([‘nslookup‘, ‘www.python.org‘])  # 创建了一个子进程并输入了 nslookup www.python.org
print(‘Exit code:‘, r)
‘‘‘
‘‘‘
#************** 如果子进程还需要输入，则可以通过communicate()方法输入
import subprocess

print(‘$ nslookup‘)
p = subprocess.Popen([‘nslookup‘], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
output, err = p.communicate(b‘set q=mx
python.org
exit
‘)
print(output.decode(‘gbk‘))      # print(output.decode(‘utf-8‘)) 源码是utf-8 但是会报错,看底下的评论是编码问题,换成gbk就好了
# 因为pycharm默认的是utf-8,这也导致了上面的例子有乱码,  ‘$ nslookup www.baidu.com‘相当于是运行在cmd中的命令，命令运行后显示的结果也是cmd中的结果，
# 而cmd本身默认编码是GBK的，所以会出现乱码。解决方法：File>>Settings>>File Encodings>>Project Encoding:（选择GBK）
print(‘Exit code:‘, p.returncode)
# 上面的代码相当于在命令行执行命令nslookup，然后手动输入：
# set q=mx
# python.org
# exit

# 输出结果如下
# $ nslookup
# Server:        192.168.19.4
# Address:    192.168.19.4#53
# 
# Non-authoritative answer:
# python.org    mail exchanger = 50 mail.python.org.
# 
# Authoritative answers can be found from:
# mail.python.org    internet address = 82.94.164.166
# mail.python.org    has AAAA address 2001:888:2000:d::a6
# 
# 
# Exit code: 0

#*************进程间通信
from multiprocessing import Process, Queue
import os, time, random

# 写数据进程执行的代码:
def write(q):
    print(‘Process to write: %s‘ % os.getpid())
    for value in [‘A‘, ‘B‘, ‘C‘]:
        print(‘Put %s to queue...‘ % value)
        q.put(value)
        time.sleep(random.random())

# 读数据进程执行的代码:
def read(q):    # 通过q 传入Queue() 队列 这样就可以保存数据了
    print(‘Process to read: %s‘ % os.getpid())
    while True:
        value = q.get(True)     # 这里的True其实是一个参数（block=True) ,表示当queue中没有数据的时候阻塞
        print(‘Get %s from queue.‘ % value)

if __name__==‘__main__‘:
    # 父进程创建Queue，并传给各个子进程：
    q = Queue()
    pw = Process(target=write, args=(q,))
    pr = Process(target=read, args=(q,))
    # 启动子进程pw，写入:
    pw.start()
    # 启动子进程pr，读取:
    pr.start()
    # 等待pw结束:
    pw.join()
    # pr进程里是死循环，无法等待其结束，只能强行终止:
    pr.terminate()