Python中greenlet和gevent使用示例

[TOC]

greenlet示例

greenlet微线程,允许在线程中手动切换

示例1,线程切换

1from greenlet import greenlet
2
3def test1(x,y):
4    z = gr2.switch(x+y)
5    print(z)
6
7def test2(u):
8    print(u)
9    gr1.switch(42)
10
11gr1 = greenlet(test1)
12gr2 = greenlet(test2)
13gr1.switch("hello",'world')

gr1和gr2是两个greenlet线程,使用gr1.switch(..)启动gr1,gr1执行test1,切换到gr2,gr2执行test2打印helloworld,然后切换回gr1,z获取到返回值42,并打印. 执行顺序为: gr1.switch("hello",'world') -> test1('hello','world')-> gr2.switch('helloword')->test2('helloworld')->print('helloworld') ->gr1.switch(42)->z=42->print(42) 打印结果:

1helloworld
242

示例2

1from greenlet import greenlet
2
3def eat(name):
4    print('%s eat 1' %name)
5    g2.switch('egon')
6    print('%s eat 2' %name)
7    g2.switch()
8def play(name):
9    print('%s play 1' %name)
10    g1.switch()
11    print('%s play 2' %name)
12
13g1=greenlet(eat)
14g2=greenlet(play)
15
16g1.switch('egon')#可以在第一次switch时传入参数，以后都不需要

gevent

gevent基于greenlet,遇到IO操作自动切换,IO操作比如网络请求,或使用 gevent.sleep(0)强制切换.

示例1

1import gevent
2
3def func1():
4    print("start func1")
5    gevent.sleep(1)
6    print("end func1")
7
8def func2():
9     print("start func2")
10    gevent.sleep(1)
11    print("end func2")
12
13gevent.joinall(
14    [
15        gevent.spawn(func1),
16        gevent.spawn(func2)
17    ]
18)

执行结果:

1start func1
2start func2
3end func1
4end func2
5``
6
7### 示例2: gevent使用monkey对所有系统自带的IO操作打patch
8```python
9from gevent import monkey;monkey.patch_all()
10
11import gevent
12import time
13def eat():
14    print('eat food 1')
15    time.sleep(2)  # 会自动的跳转到play
16    print('eat food 2')
17
18def play():
19    print('play 1')
20    time.sleep(1) # 会自动的跳转到eat
21    print('play 2')
22
23g1=gevent.spawn(eat)
24g2=gevent.spawn(play)
25gevent.joinall([g1,g2])
26print('end')

执行结果

1eat food 1
2play 1
3play 2
4eat food 2
5end

示例3,发送请求

1from gevent import monkey; monkey.patch_all()
2import gevent
3import requests
4
5def f(url):
6    print('GET: %s' % url)
7    resp = requests.get(url)
8    data = resp.text
9    print('%d bytes received from %s.' % (len(data), url))
10
11gevent.joinall([
12        gevent.spawn(f, 'https://www.python.org/'),
13        gevent.spawn(f, 'https://www.yahoo.com/'),
14        gevent.spawn(f, 'https://github.com/'),
15        gevent.spawn(f, 'https://github.com/'),
16        gevent.spawn(f, 'https://github.com/'),
17        gevent.spawn(f, 'https://github.com/'),
18        gevent.spawn(f, 'https://github.com/'),
19])

示例4:使用gevent的socket替代系统的socket

1import gevent
2from gevent import socket
3
4urls = ['www.baidu.com', 'www.163.com', 'www.qq.com']
5jobs = [gevent.spawn(socket.gethostbyname, url) for url in urls]
6gevent.joinall(jobs, timeout=2)
7
8print([job.value for job in jobs])
9
10
11或使用patch_socket()
12from gevent import monkey; monkey.patch_socket()
13import gevent
14
15def f(n):
16    for i in range(n):
17        print(gevent.getcurrent(), i)
18        gevent.sleep(0)  # 不加的话不会交替执行
19g1 = gevent.spawn(f, 5)
20g2 = gevent.spawn(f, 5)
21g3 = gevent.spawn(f, 5)
22g1.join()
23g2.join()
24g3.join()

示例5:队列中使用gevent.sleet(0)强制切换到其他线程

1import gevent
2from gevent.queue import Queue
3
4
5def func():
6    for i in range(10):
7        print("int the func")
8        q.put(f"test{i}")
9        gevent.sleep(0)
10
11def func2():
12    for i in range(10):
13        print("int the func2")
14        res = q.get()
15        print("--->",res)
16
17q = Queue()
18gevent.joinall(
19    [
20        gevent.spawn(func2),
21        gevent.spawn(func),
22    ]
23)