笔记-twisted源码-import reactor解析
1. twisted源码解析-1
twisted reactor实现原理：
第一步：
from twisted.internet import reactor
pr_type(reactor)
结果：
<twisted.internet.selectreactor.SelectReactor object at 0x0000001D5D82B748> <class 'twisted.internet.selectreactor.SelectReactor'>
1.1. twisted.internet.reactor.py源码
github中找到相应源码：
from __future__ import division, absolute_import
import sys
del sys.modules['twisted.internet.reactor']
from twisted.internet import default
default.install()
1.1.1. 问题
奇怪的是del语句，在测试时引用又删除会报错
测试代码如下：
import sys
print(sys.modules['test_unit.m1'])
del sys.modules['test_unit.m1']
报错：
KeyError: 'test_unit.m1'
复测发现是因为从del 到import m1有一个执行过程
下面的测试正常：
temp.py
from test_unit import m1
pr_type(m1)
sys.modules['test_unit.m1'] = 5
pr_type(sys.modules['test_unit.m1'])
pr_type(m1)
test_unit.m1.py
import sys
print(sys.modules['test_unit.m1'])
del sys.modules['test_unit.m1']
sys.modules['test_unit.m1'] = 6
运行temp.py结果：
<module 'test_unit.m1' from
'E:\\python\\爬虫\\scrapy\\fangchan_pro\\fangchan_code\\test_unit\\m1.py'>
6
<class 'int'>
5
<class 'int'>
6
<class 'int'>
结果释义：
在m1.py执行完成后才会执行m1 = import()的操作
这时使用locals()可以看到m1变量：'m1': 6
1.2.
twisted.internet.selectreactor.py源码
继续
def install():
"""Configure the twisted mainloop to be run using the
select() reactor.
"""
reactor = SelectReactor()
from twisted.internet.main import installReactor
installReactor(reactor)
1.3.
twisted.internet.main源码
继续：
def installReactor(reactor):
"""
Install reactor C{reactor}.
@param reactor: An object that provides one or more IReactor*
interfaces.
"""
#
this stuff should be common to all reactors.
import twisted.internet
import sys
if 'twisted.internet.reactor' in sys.modules:
raise error.ReactorAlreadyInstalledError("reactor already
installed")
twisted.internet.reactor = reactor
sys.modules['twisted.internet.reactor']
= reactor
简单来说，到这里，做了两件事
- 将系统变量reactor = SelectReactor()
- sys.modules['twisted.internet.reactor'] 设为SelectReactor()
验证如下：
import sys
pr_type(reactor)
pr_type(sys.modules['twisted.internet.reactor'])
结果：
<twisted.internet.selectreactor.SelectReactor
object at 0x000000BD4943B400> <class 'twisted.internet.selectreactor.SelectReactor'>
<twisted.internet.selectreactor.SelectReactor
object at 0x000000BD4943B400> <class
'twisted.internet.selectreactor.SelectReactor'>
1.4.
reactor.run()
reactor已经找到了，下面看一下它在运行后做什么：
res = reactor.run
pr_type(res)
结果：
<bound method _SignalReactorMixin.run of
<twisted.internet.selectreactor.SelectReactor object at
0x000000C61740B6D8>> <class 'method'>
在github中查找得到：twisted/internet/base.py
class _SignalReactorMixin(object):
def
startRunning(self, installSignalHandlers=True):
"""
PosixReactorBase的父类_SignalReactorMixin和ReactorBase都有该函数，但是_SignalReactorMixin在前，安装mro顺序的话，会先调用_SignalReactorMixin中的。
"""
self._installSignalHandlers = installSignalHandlers
ReactorBase.startRunning(self)
def run(self,
installSignalHandlers=True):
self.startRunning(installSignalHandlers=installSignalHandlers)
self.mainLoop()
def mainLoop(self):
while
self._started:
try:
while
self._started:
# Advance simulation time in delayed event
#
processors.
self.runUntilCurrent()
t2 =
self.timeout()
t =
self.running and t2
self.doIteration(t)
except:
log.msg("Unexpected error in main loop.")
log.err()
else:
log.msg('Main loop terminated.')
这里就是主循环了。