Inside Flask - Implementation of configuration

flask Configuration objects for app.config Itself is very simple to use , It's just in the form of a dictionary , And its implementation , It's in the form of a dictionary .

stay flask/config.py In file , Contains flask Configuration implementation code , There are only two classes ConfigAttribute and Config .

ConfigAttribute Represents a configuration property , Its code is just a few lines , But because of the use of descriptor Pattern , Yes python It's not easy for unfamiliar people to understand . Have a look first descriptor What is it .

descriptor Belong to python The concept of metaprogramming （ It's programming for programming ,%>_<%）, Essentially, it provides a programming protocol , That is to develop a framework for business programming （ image C# / java Reflection is also part of metaprogramming ）. Because of the nature of dynamic languages , Metaprogramming in python It's very simple to implement . As descriptor The object of , It provides a protocol for describing properties , It needs to be implemented __get__ __set__ and __delete__, To describe an object （ The described object ） How to get data 、 Set data and delete objects .

Now let's take a look at ConfigAttribute class ::

class ConfigAttribute(object):

"""Makes an attribute forward to the config"""
def __init__(self, name, get_converter=None):

self.__name__ = name

self.get_converter = get_converter
def __get__(self, obj, type=None):

if obj is None:

return self

rv = obj.config[self.__name__]

if self.get_converter is not None:

rv = self.get_converter(rv)

return rv
def __set__(self, obj, value):

obj.config[self.__name__] = value

The convention here is to define ConfigAttribute In the object of , It should contain a config Dictionaries , And then when you take a value or set a value , Change to take or set config Corresponding key Value （ stay flask Of Flask In class , contain config, Type is what we're going to see next Config class ）.

Config Class inheritance dict , It's a preservation ConfigAttribute Dictionary ::

class Config(dict):

...

meanwhile ,Config Class provides several ways to load configuration , Namely ::

from_envvar(...) # Read the to load from the environment variable py File path , And then use from_pyfile load 

from_pyfile(...) # from py Load file from file , And then use from_object load 

from_object(...) # Load from object , hold dir(obj) in , Data whose name is uppercase is loaded into self

from_json(...) # from json File loading , And then call from_mapping load 

from_mapping(...) # From multiple dictionaries , or **kwargs Parameters of form , And the data whose name is uppercase is loaded into self

When loading a file , You can use the flask Relative paths within applications （ See below ）, Or use absolute paths , Code in processing , Use both ::

filename = os.path.join(self.root_path, filename)

When the file is a relative path , I'll use the current flask app The path of the file is combined with the relative path to locate the file .

Config There are two configurations in namespace The concept of , adopt Underline Classify the parameters , It is convenient to obtain multiple configuration items at one time ::

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'

}

From the source code level , Here are a few points to pay attention to ：（1） The last thing that works from_object and from_mapping, The others are pretreatment ;（2） Configured key It should be in capitals , And then I'm going to separate them with the underscores

OK, Now look at flask How to use configuration inside .

First, in the flask/app.py Inside ,Flask Class code contains a config_class , It defaults to Config class . then config Property through make_config Generate ::

self.config = self.make_config(instance_relative_config)

and make_config The code for is as follows ::

def make_config(self, instance_relative=False):

"""Used to create the config attribute by the Flask constructor.

The `instance_relative` parameter is passed in from the constructor

of Flask (there named `instance_relative_config`) and indicates if

the config should be relative to the instance path or the root path

of the application.
.. versionadded:: 0.8

"""

root_path = self.root_path

if instance_relative:

root_path = self.instance_path

return self.config_class(root_path, self.default_config)

The concept here is instance_relative Configuration of , That is, the configuration related to the instance . If you use several in an application flask app , And these app When the configuration is different , We need to use instance related configuration , Change the current root_path Set to initialize flask app Time parameters instance_path（ Free to set ）.

self.default_config Is a default dictionary , as follows ::

default_config = ImmutableDict({

'DEBUG': get_debug_flag(default=False),

'TESTING': False,

'PROPAGATE_EXCEPTIONS': None,

'PRESERVE_CONTEXT_ON_EXCEPTION': None,

'SECRET_KEY': None,

'PERMANENT_SESSION_LIFETIME': timedelta(days=31),

'USE_X_SENDFILE': False,

...

})

And the use of ConfigAttribute The following are some of the codes for ::

debug = ConfigAttribute('DEBUG')

...

testing = ConfigAttribute('TESTING')

...

flask After setting configuration items , Users can choose according to their own needs , Modify by manipulating the dictionary 、 Update configuration ::

app.config.update({'DEBUG': False})

app.config.from_object(config_obj)

app.config.setdefault('DEBUG', False)

...

Inside Flask - Configuration of the implementation of more related articles

1. Inside Flask - json Handle

   Inside Flask - json Handle Processing web api when ,json It's a very useful data exchange format , It has a simple structure , Basically, all kinds of mainstream programming languages have good support tools . flask In dealing with json when ...

2. Inside Flask - app.py - 2

   Inside Flask - app.py - 2 Flask Initialize parameters Flass Class is Flask The core of the framework , One flask Object processing view function registration .URL The rules . Template configuration . Parameter setting and so on . commonly ...

3. Inside Flask - app.py - 1

   Inside Flask - app.py - 1 except werkzeug and jinja2 And so on ,app.py Is in Flask Of __init__.py The first one imported in Flask The mold of oneself ...

4. Inside Flask - signal Signaling mechanism

   Inside Flask - signal Signaling mechanism singal In the ordinary flask web Less contact with... In the development process , But for the use of flask When developing at the framework level , We must understand the relevant working mechanism .flas ...

5. Inside Flask - globals Global variables （ Object agent ）

   Inside Flask - globals Global variables ( Object agent ) A frame is a container , Programming within a framework , In general, it is necessary to abide by the conventions and usage patterns of the framework . The usual pattern is IoC, That is, the framework calls the user's code , Instead of the user calling the framework ...

6. Inside Flask - flask Extend the loading process

   Inside Flask - flask Extend the loading process flask Expand ( plug-in unit ) Usually with flask_< Extension name > For the extended python Package name , And when you use it , You can use import flask. ...

7. Inside Flask - flask.__init__.py And core components

   Inside Flask - flask.__init__.py And core components A simple example Let's start with a simple example . Use Flask , Usually from flask Module import Flask . request etc. ...

8. Inside Flask - Flask brief introduction

   Inside Flask - Flask brief introduction Preface Flask Our design goal is to achieve a wsgi The micro framework of , Its core code remains simple and extensible , Easy to learn . For beginners with some experience , Follow the examples and the code of some books ...

9. Chapter eight Flask To configure

   Flask It's a very flexible, small and sophisticated web frame , So where does flexibility come from ? Columns such as   Flask To configure , How to use this thing ? How convenient can it bring us ? app To configure First of all, let's show : from fl ...

Random recommendation

1. Custom browser protocol , Realization web The program calls the local program

   from   http://blog.csdn.net/talking12391239/article/details/40712759 Close test available tencent://Message/?Uin=000000 ...

2. CFgym Board Queries （ rotate 、 Flip and simplify ）

   http://codeforces.com/gym/100497 codeforces 2014-2015 CT S02E04: Codeforces Trainings Season 2 Episo ...

3. linux Modify permissions for a folder and its subfolders

   Join in -R Parameters , You can pass read and write permissions to subfolders, such as chmod -R 777 /home/mypackage that mypackage The properties of the folder and all its subfolders become 777.777 Yes. . Write . perform ...

4. Use split There is a problem with special characters during segmentation

   Use split When it's divided : String[] a="aa|bb|cc".split("|"); output: [a, a, |, b, b, |, c, c] First ...

5. Project optimization experience sharing （ 6、 ... and ）SVN Conflict and handling

   In the last blog, we shared the idea of identifying new requirements < Look at the whole situation >. Today we're going to share with you SVN Conflict resolution experience :SVN Conflict and handling ! introduction Anyone who has developed a project knows , Company development of a project will use version number control ...

6. PLSQL Developer The next error message shows garbled code

   PLSQL Developer The next error message shows garbled code Connect to the environment :win 7 Database version number :oracle 11g Simulate a mistake , See the error prompt display "????" The code problem , For example, the following : Check ...

7. Mycat Library sub-table

   Other methods : Snowflake algorithm or redis To achieve id The problem of non repetition . Database sub database sub table : Advantages and disadvantages of vertical splitting : Horizontal split : Piecewise enumeration : That is, according to the enumeration ( Defined constant ) Classified storage .

8. CSS Solution to high collapse problem

   The existence of high collapse : Cause analysis 1 <!DOCTYPE html> <html> <head> <meta charset="utf-8" /& ...

9. JS Get the last day of any month

   When getting the days of the month , Because the months are different , So the number of days per month also varies , And because of the flat leap year ,2 The number of days in the month also varies , It is very complicated to get the days of any month in the program , Here's how to solve this problem , Call this method to pass in any year and month , ...

10. 【bzoj2001】 Hnoi2010—City urban construction

    http://www.lydsy.com/JudgeOnline/problem.php?id=2001 ( Topic link ) The question Give an undirected graph ,$m$ Group operation , Modify the weight of one edge at a time , For each operation, the output is modified ...