Settings¶
Introduction¶
A typical application has some settings: if an application logs, a setting is the path to the log file. If an application sends email, there are settings to control how email is sent, such as the email address of the sender.
Applications that serve as frameworks for other applications may have
settings as well: the transaction_app
defined by
more.transaction for instance has settings controlling
transactional behavior.
Morepath has a powerful settings system that lets you define what settings are available in your application and framework. It allows an app that extends another app to override settings. This lets an app that defines a framework can also define default settings that can be overridden by the extending application if needed.
Defining a setting¶
You can define a setting using the App.setting()
directive:
@App.setting(section="logging", name="logfile")
def get_logfile():
return "/path/to/logfile.log"
You can also use this directive to override a setting in another app:
class Sub(App):
pass
@Sub.setting(section="logging", name="logfile")
def get_logfile_too():
return "/a/different/logfile.log"
Settings are grouped logically: a setting is in a section and has a
name. This way you can organize all settings that deal with logging
under the logging
section.
Accessing a setting¶
During runtime, you can access the settings of the current application
using the morepath.App.settings
property:
app.settings.logging.logfile
Remember that the current application is also accessible from the request object:
request.app.settings.logging.logfile
Defining multiple settings¶
It can be convenient to define multiple settings in a section at once.
You can do this using the App.setting_section()
directive:
@App.setting_section(section="logging")
def get_setting_section():
return {
'logfile': "/path/to/logfile.log",
'loglevel': logging.WARNING
}
You can mix setting
and setting_section
freely, but you cannot
define a setting multiple times in the same app, as this will result
in a configuration conflict.
Loading settings from a config file¶
For loading settings from a config file just load the file into a python
dictionary and pre-fill the settings with morepath.App.init_settings()
before committing the app.
A example config file with YAML syntax could look like:
# Config file for Morepath in YAML format
chameleon:
debug: true
jinja2:
auto_reload: false
autoescape: true
extensions:
- jinja2.ext.autoescape
- jinja2.ext.i18n
jwtauth:
algorithm: ES256
leeway: 20
public_key:
"MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQBWcJwPEAnS/k4kFgUhxNF7J0SQQhZG+nNgy\
+/mXwhQ5PZIUmId1a1TjkNXiKzv6DpttBqduHbz/V0EtH+QfWy0B4BhZ5MnTyDGjcz1DQqK\
dexebhzobbhSIZjpYd5aU48o9rXp/OnAnrajddpGsJ0bNf4rtMLBqFYJN6LOslAB7xTBRg="
sqlalchemy:
url: 'sqlite:///morepath.db'
transaction:
attempts: 2
You can load it with:
import yaml
with open('settings.yml') as config:
settings_dict = yaml.safe_load(config)
Remember to install pyyaml
before importing yaml
.
For example with:
$ pip install pyyaml
The same config file with JSON syntax would look like:
{
"chameleon": {
"debug": true
},
"jinja2": {
"auto_reload": false,
"autoescape": true,
"extensions": [
"jinja2.ext.autoescape",
"jinja2.ext.i18n"
]
},
"jwtauth": {
"algorithm": "ES256",
"leeway": 20,
"public_key": "MIGbMBAGByqGSM49AgEGBSuBBAAjA4GGAAQBWcJwPEAnS/k4kFgUhxNF7J0SQQhZG+nNgy+/mXwhQ5PZIUmId1a1TjkNXiKzv6DpttBqduHbz/V0EtH+QfWy0B4BhZ5MnTyDGjcz1DQqKdexebhzobbhSIZjpYd5aU48o9rXp/OnAnrajddpGsJ0bNf4rtMLBqFYJN6LOslAB7xTBRg="
},
"sqlalchemy": {
"url": "sqlite:///morepath.db"
},
"transaction": {
"attempts": 2
}
}
To load it use:
import json
with open('settings.json') as config:
settings_dict = json.load(config)
Now register the settings dictionary in the App settings before starting the App:
App.init_settings(settings_dict)
morepath.commit(App)
app = App()
You can access the settings as before:
>>> app.settings.jinja2.extensions
['jinja2.ext.autoescape', 'jinja2.ext.i18n']
>>> app.settings.jwtauth.algorithm
'ES256'
>>> app.settings.sqlalchemy.url
'sqlite:///morepath.db'
You can also override and extend the settings by loading a config file in an extending app as usual.