FLASK類

config 配置源碼解讀

構(gòu)建一個(gè)app應(yīng)用

示例代碼

from flask import Flask
import os

#定義一個(gè)配置類
class development():
    SECRET_KEY = os.environ.get('SECRET_KEY') or os.urandom(24)
    SQLALCHEMY_COMMIT_ON_TEARDOWN = True
    SQLALCHEMY_TRACK_MODIFICATIONS = True

#把配置類放到字典里
config = {
    "dev": development
}

app = Flask(__name__)

app.config.from_object(config['dev'])

print(app.config)


@app.route('/')
def hello_world():
    return 'Hello World!'


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

app是Flask類的實(shí)例,以下是Flask類的與config相關(guān)的源碼

# 定義了一個(gè)默認(rèn)的配置字典
default_config = ImmutableDict(
        {
            ...
            "SECRET_KEY": None,
            ...
        }
      )
class Flask(_PackageBoundObject):
    ...
    self.config = self.make_config(instance_relative_config)
    # app的config 由make_config方法處理
    ...
    def make_config(self, instance_relative=False):
        ...
        root_path = self.root_path #這里的root_path 是None
        if instance_relative: # 這里是False
            root_path = self.instance_path
        defaults = dict(self.default_config)
        defaults["ENV"] = get_env()
        defaults["DEBUG"] = get_debug_flag()
        return self.config_class(root_path, defaults) 

繼續(xù)找這里返回的config_class,由下面代碼可以看出實(shí)際上返回了一個(gè)默認(rèn)配置的字典defaults，就是上面定義的那個(gè),這個(gè)時(shí)候的app.config就是一個(gè)字典default_config

app.config.form_object(config['dev'],這里config['dev']是一個(gè)字典,看from_object做了什么工作,這個(gè)函數(shù)從config['dev']這個(gè)字典里拿出配置的參數(shù),如果原來(lái)默認(rèn)字典里有的就修改,沒(méi)有的就添加.

config_class = Config
    
    class Config(dict):
        def __init__(self, root_path, defaults=None):
            dict.__init__(self, defaults or {})
            self.root_path = root_path
    
        def from_object(self, obj):
            if isinstance(obj, string_types): #這里的obj是一個(gè)字符串
                obj = import_string(obj) #這里是可以從一個(gè)py文件導(dǎo)入的邏輯
            for key in dir(obj): #這里的obj是一個(gè)字典
                if key.isupper(): #配置字典里的配置項(xiàng)要大寫(xiě)的才能獲取到
                    self[key] = getattr(obj, key)
        
    def get_env():
        """Get the environment the app is running in, indicated by the
        :envvar:`FLASK_ENV` environment variable. The default is
        ``'production'``.
        """
        return os.environ.get("FLASK_ENV") or "production"

utils里的import_string方法

def import_string(import_name, silent=False):
    # force the import name to automatically convert to strings
    # __import__ is not able to handle unicode strings in the fromlist
    # if the module is a package
    import_name = str(import_name).replace(":", ".")
    try:
        try:
            __import__(import_name)
        except ImportError:
            if "." not in import_name:
                raise
        else:
            return sys.modules[import_name]

        module_name, obj_name = import_name.rsplit(".", 1)
        module = __import__(module_name, globals(), locals(), [obj_name])
        try:
            return getattr(module, obj_name)
        except AttributeError as e:
            raise ImportError(e)

    except ImportError as e:
        if not silent:
            reraise(
                ImportStringError, ImportStringError(import_name, e), sys.exc_info()[2]
            )