Python中greenlet和gevent使用示例

目录

• greenlet示例
  • 示例1,线程切换
  • 示例2
• gevent
  • 示例1
  • 示例3,发送请求
  • 示例4:使用gevent的socket替代系统的socket
  • 示例5:队列中使用gevent.sleet(0)强制切换到其他线程

greenlet示例

greenlet微线程,允许在线程中手动切换

示例1,线程切换

from greenlet import greenlet

def test1(x,y):
    z = gr2.switch(x+y)
    print(z)

def test2(u):
    print(u)
    gr1.switch(42)

gr1 = greenlet(test1)
gr2 = greenlet(test2)
gr1.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:

helloworld
42

示例2

from greenlet import greenlet

def eat(name):
    print('%s eat 1' %name)
    g2.switch('egon')
    print('%s eat 2' %name)
    g2.switch()
def play(name):
    print('%s play 1' %name)
    g1.switch()
    print('%s play 2' %name)

g1=greenlet(eat)
g2=greenlet(play)

g1.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

import gevent

def func1():
    print("start func1")
    gevent.sleep(1)
    print("end func1")

def func2():
     print("start func2")
    gevent.sleep(1)
    print("end func2")

gevent.joinall(
    [
        gevent.spawn(func1),
        gevent.spawn(func2)
    ]
)

执行结果:

start func1
start func2
end func1
end func2
``

### 示例2: gevent使用monkey对所有系统自带的IO操作打patch
```python
from gevent import monkey;monkey.patch_all()

import gevent
import time
def eat():
    print('eat food 1')
    time.sleep(2)  # 会自动的跳转到play
    print('eat food 2')

def play():
    print('play 1')
    time.sleep(1) # 会自动的跳转到eat
    print('play 2')

g1=gevent.spawn(eat)
g2=gevent.spawn(play)
gevent.joinall([g1,g2])
print('end')

执行结果

eat food 1
play 1
play 2
eat food 2
end

示例3,发送请求

from gevent import monkey; monkey.patch_all()
import gevent
import requests

def f(url):
    print('GET: %s' % url)
    resp = requests.get(url)
    data = resp.text
    print('%d bytes received from %s.' % (len(data), url))

gevent.joinall([
        gevent.spawn(f, 'https://www.python.org/'),
        gevent.spawn(f, 'https://www.yahoo.com/'),
        gevent.spawn(f, 'https://github.com/'),
        gevent.spawn(f, 'https://github.com/'),
        gevent.spawn(f, 'https://github.com/'),
        gevent.spawn(f, 'https://github.com/'),
        gevent.spawn(f, 'https://github.com/'),
])

示例4:使用gevent的socket替代系统的socket

import gevent
from gevent import socket

urls = ['www.baidu.com', 'www.163.com', 'www.qq.com']
jobs = [gevent.spawn(socket.gethostbyname, url) for url in urls]
gevent.joinall(jobs, timeout=2)

print([job.value for job in jobs])


或使用patch_socket()
from gevent import monkey; monkey.patch_socket()
import gevent

def f(n):
    for i in range(n):
        print(gevent.getcurrent(), i)
        gevent.sleep(0)  # 不加的话不会交替执行
g1 = gevent.spawn(f, 5)
g2 = gevent.spawn(f, 5)
g3 = gevent.spawn(f, 5)
g1.join()
g2.join()
g3.join()

示例5:队列中使用gevent.sleet(0)强制切换到其他线程

import gevent
from gevent.queue import Queue


def func():
    for i in range(10):
        print("int the func")
        q.put(f"test{i}")
        gevent.sleep(0)

def func2():
    for i in range(10):
        print("int the func2")
        res = q.get()
        print("--->",res)

q = Queue()
gevent.joinall(
    [
        gevent.spawn(func2),
        gevent.spawn(func),
    ]
)