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Python-based singleton configuration

Project description

This module provides python based configuration that is stored in a singleton object to ensure consistency across your project.

Command Line

Pyconfig has a command line utility that lets you inspect your project to find all the configuration keys defined.

$ pyconfig -h
usage: pyconfig [-h] [-f F | -m M] [-v] [-l] [-a | -k] [-n] [-s] [-c]

Helper for working with pyconfigs

optional arguments:
  -h, --help          show this help message and exit
  -f F, --filename F  parse an individual file or directory
  -m M, --module M    parse a package or module, recursively looking inside it
  -v, --view-call     show the actual pyconfig call made (default: show namespace)
  -l, --load-configs  query the currently set value for each key found
  -a, --all           show keys which don't have defaults set
  -k, --only-keys     show a list of discovered keys without values
  -n, --natural-sort  sort by filename and line (default: alphabetical by key)
  -s, --source        show source annotations (implies --natural-sort)
  -c, --color         toggle output colors (default: True)

Example output

$ pyconfig --file .
humbledb.allow_explicit_request = True
humbledb.auto_start_request = True
humbledb.connection_pool = 300
humbledb.tz_aware = True
humbledb.use_greenlets = False
humbledb.write_concern = 1

$ pyconfig --view-call --file .
pyconfig.get('humbledb.allow_explicit_request', True)
pyconfig.setting('humbledb.auto_start_request', True)
pyconfig.setting('humbledb.connection_pool', 300)
pyconfig.setting('humbledb.tz_aware', True)
pyconfig.setting('humbledb.use_greenlets', False)
pyconfig.setting('humbledb.write_concern', 1)

$ pyconfig --source --file .
# ./humbledb/mongo.py, line 98
humbledb.allow_explicit_request = True
# ./humbledb/mongo.py, line 178
humbledb.connection_pool = 300
# ./humbledb/mongo.py, line 181
humbledb.auto_start_request = True
# ./humbledb/mongo.py, line 185
humbledb.use_greenlets = False
# ./humbledb/mongo.py, line 188
humbledb.tz_aware = True
# ./humbledb/mongo.py, line 191
humbledb.write_concern = 1

Code Examples

The most basic usage allows you to get, retrieve and modify values. Pyconfig’s singleton provides convenient accessor methods for these actions:

>>> import pyconfig
>>> pyconfig.get('my.setting', 'default')
'default'
>>> pyconfig.set('my.setting', 'new')
>>> pyconfig.get('my.setting', 'default')
'new'
>>> pyconfig.reload(clear=True)
>>> pyconfig.get('my.setting', 'default')
'default'

Pyconfig also provides shortcuts for giving classes property descriptors which map to the current setting stored in the singleton:

>>> import pyconfig
>>> class MyClass(object):
...     my_setting = pyconfig.setting('my.setting', 'default')
...
>>> MyClass.my_setting
'default'
>>> MyClass().my_setting
'default'
>>> pyconfig.set('my.setting', "Hello World!")
>>> MyClass.my_setting
'Hello World!'
>>> MyClass().my_setting
'Hello World!'
>>> pyconfig.reload(clear=True)
>>> MyClass.my_setting
'default'

Pyconfig allows you to override settings via a python configuration file, that defines its configuration keys as a module namespace. By default, Pyconfig will look on your PYTHONPATH for a module named localconfig, and if it exists, it will use this module namespace to update all configuration settings:

# __file__ = "$PYTHONPATH/localconfig.py"
from pyconfig import Namespace

# Namespace objects allow you to use attribute assignment to create setting
# key names
my = Namespace()
my.setting = 'from_localconfig'
# Namespace objects implicitly return new nested Namespaces when accessing
# attributes that don't exist
my.nested.setting = 'also_from_localconfig'

With a localconfig on the PYTHONPATH, it will be loaded before any settings are read:

>>> import pyconfig
>>> pyconfig.get('my.setting')
'from_localconfig'
>>> pyconfig.get('my.nested.setting')
'also_from_localconfig'

Pyconfig also allows you to create distutils plugins that are automatically loaded. An example setup.py:

# __file__ = setup.py
from setuptools import setup

setup(
        name='pytest',
        version='0.1.0-dev',
        py_modules=['myconfig', 'anyconfig'],
        entry_points={
            # The "my" in "my =" indicates a base namespace to use for
            # the contained configuration. If you do not wish a base
            # namespace, use "any"
            'pyconfig':[
                  'my = myconfig',
                  'any = anyconfig',
                  ],
            },
        )

An example distutils plugin configuration file:

# __file__ = myconfig.py
from pyconfig import Namespace

def some_callable():
    print "This callable was called."
    print "You can execute any arbitrary code."

setting = 'from_plugin'
nested = Namespace()
nested.setting = 'also_from_plugin'

Another example configuration file, without a base namespace:

# __file__ = anyconfig.py
from pyconfig import Namespace
other = Namespace()
other.setting = 'anyconfig_value'

Showing the plugin-specified settings:

>>> import pyconfig
>>> pyconfig.get('my.setting', 'default')
This callable was called.
You can execute any arbitrary code.
'from_plugin'
>>> pyconfig.get('my.nested.setting', 'default')
'also_from_plugin'
>>> pyconfig.get('other.setting', 'default')
'anyconfig_value'

More fancy stuff:

>>> # Reloading changes re-calls functions...
>>> pyconfig.reload()
This callable was called.
You can execute any arbitrary code.
>>> # This can be used to inject arbitrary code by changing a
>>> # localconfig.py or plugin and reloading a config... especially
>>> # when pyconfig.reload() is attached to a signal
>>> import signal
>>> signal.signal(signal.SIGUSR1, pyconfig.reload)

Pyconfig provides a @reload_hook decorator that allows you to register functions or methods to be called when the configuration is reloaded:

>>> import pyconfig
>>> @pyconfig.reload_hook
... def reload():
...     print "Do something here."
...
>>> pyconfig.reload()
Do something here.
warning:It should not be used to register large numbers of functions (e.g. registering a bound method in a class’s __init__ method), since there is no way to un-register a hook and it will cause a memory leak, since a bound method maintains a strong reference to the bound instance.
note:Because the reload hooks are called without arguments, it will not work with unbound methods or classmethods.

Changes

This section contains descriptions of changes in each new version.

2.1.0

  • Pyconfig now works on Python 3, thanks to hfalcic <https://github.com/hfalcic>!

2.0.0

  • Pyconfig now has the ability to show you what config keys are defined in a directory.

1.2.0

  • No longer uses Python 2.7 format(). Should work on 2.6 and maybe earlier.

1.1.2

  • Move version string into pyconfig.__version__

1.1.1

  • Fix bug with setup.py that prevented installation

1.1.0

  • Allow for implicitly nesting Namespaces when accessing attributes that are undefined

Contributors

  • shakefu <http://github.com/shakefu> - Creator and maintainer
  • hfalcic <https://github.com/hfalcic>

Project details


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