记录Tornado-4.0.2源码的阅读，学习，分析
options.py
1. imports 部分
1.1 __future__
1 from __future__ import absolute_import, division, print_function, with_statement
future_statement 即：from __futuren import XXX. 参见
1.2 other imports from Python Library
1 import datetime2 import numbers3 import re4 import sys5 import os6 import textwrap
1.3 other imports from tornado
1 from tornado.escape import _unicode2 from tornado.log import define_logging_options3 from tornado import stack_context4 from tornado.util import basestring_type, exec_in
2. 定义的类
2.1 OptionParser类
该类负责解析命令行的Option, 每个option被抽象为类_Option的对象。
2.2 _Option类
代表命令行上的每个option，该类为内部类。
2.3 全局的OptionParser对象
定义了一个全局的OptionParser对象。options.py提供的接口都是在该对象上进行操作的。
末尾调用了以下接口来将log相关的option添加到options.py模块中。
1 define_logging_options(options)
3. options.py对外提供的接口
[Todo]
3.1 define
1 def define(name, default=None, type=None, help=None, metavar=None,2 multiple=False, group=None, callback=None)
3.2 parse_command_line
1 def parse_config_file(path, final=True)
Learn From options.py
1. sys模块
import sys
https://docs.python.org/2/library/sys.html?highlight=sys#module-sys
sys._getframe([depth])
"Return a frame object from the call stack. If optional integer depth is given, return the frame
object that many calls below the top of the stack. If that is deeper than the call stack,
is raised. The default fordepth is zero, returning the frame at the top of the call stack."
在options.py中的使用，在OptionParser类的define方法的实现中：
1 frame = sys._getframe(0)
2. inspect 模块
https://docs.python.org/2/library/inspect.html
"The module provides several useful functions to help get information about live
objects such as modules, classes, methods, functions, tracebacks, frame objects, and code objects. "
该模块中包含 frame 类型(即: sys._getframe() 返回值的类型 )的说明。
3. unittest.mock.patch
mock 模块
Python中的单元测试。
4. 不了解的语法
4.1 return xxxx if yyyy else zzzz
1 def value(self):2 return self.default if self._value is _Option.UNSET else self._value
4.2 xxx for yyy, zzz in ttt
1 _TIMEDELTA_ABBREV_DICT = dict(2 (abbrev, full) for full, abbrevs in _TIMEDELTA_ABBREVS3 for abbrev in abbrevs)
4.3 正则表达式
1 _FLOAT_PATTERN = r'[-+]?(?:\d+(?:\.\d*)?|\.\d+)(?:[eE][-+]?\d+)?'
Reference
1. http://www.tornadoweb.org/en/stable/options.html