Configuring Pecan Applications¶
Pecan is very easy to configure. As long as you follow certain conventions, using, setting and dealing with configuration should be very intuitive.
Pecan configuration files are pure Python. Each “section” of the configuration is a dictionary assigned to a variable name in the configuration module.
Default Values¶
Below is the complete list of default values the framework uses:
server = {
'port' : '8080',
'host' : '0.0.0.0'
}
app = {
'root' : None,
'modules' : [],
'static_root' : 'public',
'template_path' : ''
}
Application Configuration¶
The app
configuration values are used by Pecan to wrap your
application into a valid WSGI app. The app
configuration
is specific to your application, and includes values like the root
controller class location.
A typical application configuration might look like this:
app = {
'root' : 'project.controllers.root.RootController',
'modules' : ['project'],
'static_root' : '%(confdir)s/public',
'template_path' : '%(confdir)s/project/templates',
'debug' : True
}
Let’s look at each value and what it means:
- modules
- A list of modules where pecan will search for applications.
Generally this should contain a single item, the name of your
project’s python package. At least one of the listed modules must
contain an
app.setup_app
function which is called to create the WSGI app. In other words, this package should be where yourapp.py
file is located, and this file should contain asetup_app
function. - root
- The root controller of your application. Remember to provide a
string representing a Python path to some callable (e.g.,
"yourapp.controllers.root.RootController"
). - static_root
- The directory where your static files can be found (relative to the project root). Pecan comes with middleware that can be used to serve static files (like CSS and Javascript files) during development.
- template_path
- Points to the directory where your template files live (relative to the project root).
- debug
- Enables the ability to display tracebacks in the browser and interactively debug during development.
Warning
app
is a reserved variable name for that section of the
configuration, so make sure you don’t override it.
Warning
Make sure debug is always set to False
in production environments.
See also
Server Configuration¶
Pecan provides some sane defaults. Change these to alter the host and port your WSGI app is served on.
server = {
'port' : '8080',
'host' : '0.0.0.0'
}
Additional Configuration¶
Your application may need access to other configuration values at runtime (like third-party API credentials). Put these settings in their own blocks in your configuration file.
twitter = {
'api_key' : 'FOO',
'api_secret' : 'SECRET'
}
Accessing Configuration at Runtime¶
You can access any configuration value at runtime via pecan.conf
.
This includes custom, application, and server-specific values.
For example, if you needed to specify a global administrator, you could do so like this within the configuration file.
administrator = 'foo_bar_user'
And it would be accessible in pecan.conf
as:
>>> from pecan import conf
>>> conf.administrator
'foo_bar_user'
Dictionary Conversion¶
In certain situations you might want to deal with keys and values, but in strict
dictionary form. The Config
object has a helper
method for this purpose that will return a dictionary representation of the
configuration, including nested values.
Below is a representation of how you can access the
to_dict()
method and what it returns as
a result (shortened for brevity):
>>> from pecan import conf
>>> conf
Config({'app': Config({'errors': {}, 'template_path': '', 'static_root': 'public', [...]
>>> conf.to_dict()
{'app': {'errors': {}, 'template_path': '', 'static_root': 'public', [...]
Prefixing Dictionary Keys¶
to_dict()
allows you to pass an optional
string argument if you need to prefix the keys in the returned dictionary.
>>> from pecan import conf
>>> conf
Config({'app': Config({'errors': {}, 'template_path': '', 'static_root': 'public', [...]
>>> conf.to_dict('prefixed_')
{'prefixed_app': {'prefixed_errors': {}, 'prefixed_template_path': '', 'prefixed_static_root': 'prefixed_public', [...]
Dotted Keys, Non-Python Idenfitiers, and Native Dictionaries¶
Sometimes you want to specify a configuration option that includes dotted keys
or is not a valid Python idenfitier, such as ()
. These situations are
especially common when configuring Python logging. By passing a special key,
__force_dict__
, individual configuration blocks can be treated as native
dictionaries.
logging = {
'root': {'level': 'INFO', 'handlers': ['console']},
'loggers': {
'sqlalchemy.engine': {'level': 'INFO', 'handlers': ['console']},
'__force_dict__': True
},
'formatters': {
'custom': {
'()': 'my.package.customFormatter'
}
}
}
from myapp import conf
assert isinstance(conf.logging.loggers, dict)
assert isinstance(conf.logging.loggers['sqlalchemy.engine'], dict)