Flask之配置文件

一、配置文件概述

Flask中的配置参数有很多，它是flask中flask.config.Config对象（继承字典）：

class Config(dict):
    """Works exactly like a dict but provides ways to fill it from files
    or special dictionaries.  There are two common patterns to populate the
    config.

    Either you can fill the config from a config file::

        app.config.from_pyfile('yourconfig.cfg')

    Or alternatively you can define the configuration options in the
    module that calls :meth:`from_object` or provide an import path to
    a module that should be loaded.  It is also possible to tell it to
    use the same module and with that provide the configuration values
    just before the call::

        DEBUG = True
        SECRET_KEY = 'development key'
        app.config.from_object(__name__)

    In both cases (loading from any Python file or loading from modules),
    only uppercase keys are added to the config.  This makes it possible to use
    lowercase values in the config file for temporary values that are not added
    to the config or to define the config keys in the same file that implements
    the application.

    Probably the most interesting way to load configurations is from an
    environment variable pointing to a file::

        app.config.from_envvar('YOURAPPLICATION_SETTINGS')

    In this case before launching the application you have to set this
    environment variable to the file you want to use.  On Linux and OS X
    use the export statement::

        export YOURAPPLICATION_SETTINGS='/path/to/config/file'

    On windows use `set` instead.

    :param root_path: path to which files are read relative from.  When the
                      config object is created by the application, this is
                      the application's :attr:`~flask.Flask.root_path`.
    :param defaults: an optional dictionary of default values
    """

    def __init__(self, root_path, defaults=None):
        dict.__init__(self, defaults or {})
        self.root_path = root_path

    def from_envvar(self, variable_name, silent=False):
        """Loads a configuration from an environment variable pointing to
        a configuration file.  This is basically just a shortcut with nicer
        error messages for this line of code::

            app.config.from_pyfile(os.environ['YOURAPPLICATION_SETTINGS'])

        :param variable_name: name of the environment variable
        :param silent: set to ``True`` if you want silent failure for missing
                       files.
        :return: bool. ``True`` if able to load config, ``False`` otherwise.
        """
        rv = os.environ.get(variable_name)
        if not rv:
            if silent:
                return False
            raise RuntimeError(
                "The environment variable %r is not set "
                "and as such configuration could not be "
                "loaded.  Set this variable and make it "
                "point to a configuration file" % variable_name
            )
        return self.from_pyfile(rv, silent=silent)

    def from_pyfile(self, filename, silent=False):
        """Updates the values in the config from a Python file.  This function
        behaves as if the file was imported as module with the
        :meth:`from_object` function.

        :param filename: the filename of the config.  This can either be an
                         absolute filename or a filename relative to the
                         root path.
        :param silent: set to ``True`` if you want silent failure for missing
                       files.

        .. versionadded:: 0.7
           `silent` parameter.
        """
        filename = os.path.join(self.root_path, filename)
        d = types.ModuleType("config")
        d.__file__ = filename
        try:
            with open(filename, mode="rb") as config_file:
                exec(compile(config_file.read(), filename, "exec"), d.__dict__)
        except IOError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR, errno.ENOTDIR):
                return False
            e.strerror = "Unable to load configuration file (%s)" % e.strerror
            raise
        self.from_object(d)
        return True

    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)

        Nothing is done to the object before loading. If the object is a
        class and has ``@property`` attributes, it needs to be
        instantiated before being passed to this method.

        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)

    def from_json(self, filename, silent=False):
        """Updates the values in the config from a JSON file. This function
        behaves as if the JSON object was a dictionary and passed to the
        :meth:`from_mapping` function.

        :param filename: the filename of the JSON file.  This can either be an
                         absolute filename or a filename relative to the
                         root path.
        :param silent: set to ``True`` if you want silent failure for missing
                       files.

        .. versionadded:: 0.11
        """
        filename = os.path.join(self.root_path, filename)

        try:
            with open(filename) as json_file:
                obj = json.loads(json_file.read())
        except IOError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
                return False
            e.strerror = "Unable to load configuration file (%s)" % e.strerror
            raise
        return self.from_mapping(obj)

    def from_mapping(self, *mapping, **kwargs):
        """Updates the config like :meth:`update` ignoring items with non-upper
        keys.

        .. versionadded:: 0.11
        """
        mappings = []
        if len(mapping) == 1:
            if hasattr(mapping[0], "items"):
                mappings.append(mapping[0].items())
            else:
                mappings.append(mapping[0])
        elif len(mapping) > 1:
            raise TypeError(
                "expected at most 1 positional argument, got %d" % len(mapping)
            )
        mappings.append(kwargs.items())
        for mapping in mappings:
            for (key, value) in mapping:
                if key.isupper():
                    self[key] = value
        return True

    def get_namespace(self, namespace, lowercase=True, trim_namespace=True):
        """Returns a dictionary containing a subset of configuration options
        that match the specified namespace/prefix. Example usage::

            app.config['IMAGE_STORE_TYPE'] = 'fs'
            app.config['IMAGE_STORE_PATH'] = '/var/app/images'
            app.config['IMAGE_STORE_BASE_URL'] = 'http://img.website.com'
            image_store_config = app.config.get_namespace('IMAGE_STORE_')

        The resulting dictionary `image_store_config` would look like::

            {
                'type': 'fs',
                'path': '/var/app/images',
                'base_url': 'http://img.website.com'
            }

        This is often useful when configuration options map directly to
        keyword arguments in functions or class constructors.

        :param namespace: a configuration namespace
        :param lowercase: a flag indicating if the keys of the resulting
                          dictionary should be lowercase
        :param trim_namespace: a flag indicating if the keys of the resulting
                          dictionary should not include the namespace

        .. versionadded:: 0.11
        """
        rv = {}
        for k, v in iteritems(self):
            if not k.startswith(namespace):
                continue
            if trim_namespace:
                key = k[len(namespace) :]
            else:
                key = k
            if lowercase:
                key = key.lower()
            rv[key] = v
        return rv

    def __repr__(self):
        return "<%s %s>" % (self.__class__.__name__, dict.__repr__(self))

内置配置参数：

ENV #应用运行于什么环境，在生产环境中不要使用 development 。缺省值： 'production'
DEBUG #是否开启调试模式，在生产环境中不要开启调试模式。缺省值：当 ENV 是 'development' 时，为 True ；否则为 False 。
TESTING #开启测试模式。缺省值： False
PROPAGATE_EXCEPTIONS #当异常发生时，不要弹出请求情境。缺省值： None
TRAP_HTTP_EXCEPTIONS #如果没有处理 HTTPException 类型异常的处理器，重新引发该异常用于被 交互调试器处理，
　　　　　　　　　　　　　　而不是作为一个简单的错误响应来返回。缺省值： False
TRAP_BAD_REQUEST_ERRORS #尝试操作一个请求字典中不存在的键，如 args 和 form ，会返回一个 
　　　　　　　　　　　　　　400 Bad Request error 页面。缺省值： None
SECRET_KEY #密钥用于会话 cookie 的安全签名，并可用于应用或者扩展的其他安全需求。缺省值： None
SESSION_COOKIE_NAME #会话 cookie 的名称。假如已存在同名 cookie ，本变量可改变。缺省值： 'session'
SESSION_COOKIE_DOMAIN #认可会话 cookie 的域的匹配规则。缺省值： None
SESSION_COOKIE_PATH #认可会话 cookie 的路径。缺省值： None
SESSION_COOKIE_HTTPONLY #为了安全，浏览器不会允许 JavaScript 操作标记为“ HTTP only ”的 cookie 。缺省值： True
SESSION_COOKIE_SECURE #如果 cookie 标记为“ secure ”，那么浏览器只会使用基于 HTTPS 的请求发 送 cookie 。缺省值： False
SESSION_COOKIE_SAMESITE #限制来自外部站点的请求如何发送 cookie 。缺省值： None
PERMANENT_SESSION_LIFETIME #如果 session.permanent 为真， cookie 的有效期为本变量设置的数字， 单位为秒。
　　　　　　　　　　　　　　　　　缺省值： timedelta(days=31) （ 2678400 秒）
SESSION_REFRESH_EACH_REQUEST #当 session.permanent 为真时，控制是否每个响应都发送 cookie 。缺省值： True
SERVER_NAME #通知应用其所绑定的主机和端口。子域路由匹配需要本变量。缺省值： None
APPLICATION_ROOT #通知应用应用的根路径是什么。缺省值： '/'
...

上面是一部分的内置的配置参数，配置文件可有下面三种方式。

二、直接配置

from flask import Flask

app = Flask(__name__)

#直接配置
app.config['DEBUG'] = True
app.config['SECRET_KEY'] = 'ab32j56kgfsl_k'


@app.route('/')
def index():
    return 'index'

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

三、from_pyfile

导入一个.py文件：

from flask import Flask

app = Flask(__name__)

# 导入py文件
app.config.from_pyfile('settings.py') # settings.py路径


@app.route('/')
def index():
    return 'index'


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

settings.py中的内容如下：

# settings.py
DEBUG = True

四、from_object

 导入一个对象：

from flask import Flask

app = Flask(__name__)

# 导入一个类的路径
app.config.from_object('"settings.DevelopmentConfig"')


@app.route('/')
def index():
    return 'index'


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

settings.py文件中：

class Config(object):
    DEBUG = False
    DATABASE_URI = 'sqlite://...'


class ProductionConfig(Config):
    DATABASE_URI = 'mysql://...'


class DevelopmentConfig(Config):
    DEBUG = True