flask学习：如何从config里载入配置

代码如下：

1.main.py

from flask import Flask
from config import DevConfig

app=Flask(__name__)

app.config.from_object(DevConfig)

@app.route('/')
def home():
    return "<h1>Hello Wcf!</h1>"

if __name__=='__main__':
    app.run()

2.config.py

class Config(object):
    pass

class ProdConfig(Config):
    pass

class DevConfig(Config):
    DEBUG=True

　想了解一下，app.config.from_boject...是如何运作的，跟踪到源代码中：

在flask的config.py中，有一个方法，是：

    def from_object(self, obj):
        """Updates the values from the given object.  An object can be of one
        of the following two types:

        -   a string: in this case the object with that name will be imported
        -   an actual object reference: that object is used directly

        Objects are usually either modules or classes. :meth:`from_object`
        loads only the uppercase attributes of the module/class. A ``dict``
        object will not work with :meth:`from_object` because the keys of a
        ``dict`` are not attributes of the ``dict`` class.

        Example of module-based configuration::

            app.config.from_object('yourapplication.default_config')
            from yourapplication import default_config
            app.config.from_object(default_config)

        You should not use this function to load the actual configuration but
        rather configuration defaults.  The actual config should be loaded
        with :meth:`from_pyfile` and ideally from a location not within the
        package because the package might be installed system wide.

        See :ref:`config-dev-prod` for an example of class-based configuration
        using :meth:`from_object`.

        :param obj: an import name or object
        """
        if isinstance(obj, string_types):
            obj = import_string(obj)
        for key in dir(obj):
            if key.isupper():
                self[key] = getattr(obj, key)

　　这里，用到了一个dir的python自带的函数，是其代码的关键，那么，dir是干嘛用的么？

在python中任何东西都是对像，一种数据类型，一个模块等，都有自己的属性和方法，除了常用方法外，其它的你不需要全部记住它，交给dir()函数就好了。

dir()函数操作方法很简单，只需要把你想要查询和对像添写到( )括号中就可以使用了。