ConfigManager

There are numerous method for persisting application configuration data in Python:

• Windows style 'INI' files
• Binary blobs
• XML/YAML/JSON formatted files

This small project provides two simple classes to persist application data without the user needing to provide anything other than a destination file path and (possibly) a list of items to persist:

• ConfigManager: A class that can be used for CLI and non-GUI apps.
• QTConfigManager: A class that can be used with QT5 app to persist/restore specific active GUI elements.

ConfigManager (CM) is a Python class to trivialise persisting app data from CLI or GUI applications. Your application merely creates an instance of ConfigManager, creates and assigns values to its attributes and calls 'save_config' (as it closes) to write the data to the configuration file. Subsequent runs of your appliction will read the configuration file on startup, and re-create the previous attributes with the previous values.

Internally, ConfigManager uses JSON to store it's data. New attributes can be created as normal by simple assignment. If you try to assign a non-existent attribute to a variable with =, it will assign 'None' rather than generate an exception. You can use CM.assign('attrb', DefaultValue) to simultaneously create and assign an attribute - if it doesn't already exist (current value is None), the default value is used. Attributes can be any normal Python data type¹ and all attributes are saved except private ones (attributes starting with '_'), with the exception of _comment, which can be used as a header for the saved config.

QTConfigManager (QM) is a similar python class but extended to specifically persist/restore the values of QT5 GUI elements. This can be used to save/restore the complete state of GUI based applications between different runs, users etc. A simple list of the GUI item names is sufficient to identify the items to persist.

Notes:

1. Only widgets from one form can currently be saved automatically, though its quite feasible to save/restore widgets from other forms individually as additional QM.attributes, see last example.
2. You can use save_qt() and restore_qt() to temporarily save/restore state in a running application
3. Only QT5 (PyQT) framework is supported, though it should be relatively straightforwards to swap this for TKinter, WxPython or PyGObject support.
4. Only the most common QT5 widgets are currently supported, but others can be added as required.

Example Usage

Basic config file

import ConfigManager
...
# Creates a configuration file at /home/$USER/.config/MyApp/myapp.config
config = ConfigManager('MyApp', 'myapp')

# Basic assign values
config.user = "Mike"
config.position = {'X': 24.5, 'Y': -16.1}

# and save
config.save_config()

Better usage - accepts persisted data on re-start

# Create/use configuration file at /home/$USER/.config/MyApp/myapp.config
config = ConfigManager('MyApp', 'myapp')
# Now, after creation, config.user is 'Mike' and config.position is {'X': 24.5 ...

# Assign default value 'Dave' if config.user doesn't already exist
config.user = config.assign("user", "Dave")  # config.user is aready set to 'Mike'

# Assign new default value if config.position doesn't exist
global_position = config.assign(config.position, {'X': 0.00, 'Y': 0.00})
# Both global_position and config.position are unchanged at {'X':24.5...
 
config._counter = 100   # Won't be saved with configuration file

global_uid = config.uid  # config.uid doesn't exist yet so both global_uid and config.uid are set None
global_guid = config.assign('guid', 12345678) # Both global_guid and config.guid set 12345678
# or simply
config.assign('another_guid', 987654321) # Initialises config.another_guid if it doesn't already exist

# and save
config.save_config()

QTConfigManager example

import QTConfigManager
...
WDGT_LIST = ['cbComboBox', 'leLineEdit', 'rbRadioBtn1',...] # List of QT5 widgets to save

# Create/use configuration file at /home/$USER/.config/MyApp/myguiapp.config
qt_config = QTConfigManager(self, 'MyApp', 'myguiapp') # self is owner of widgets

# Change the comment
qt_config._comment = "MyGUIApp: DO NOT HAND EDIT"  #  Appears at the top of the saved file

# Load list of items to save if not found (1st run)
qt_config.assign('ui_list', WDGT_LIST)
...
# and save
qt_config.save_config()

Saving GUI items from secondary form

WDGT_LIST = ['cbComboBox', 'leLineEdit', 'rbRadioBtn1',...] # List of QT5 widgets to save
# Create/use configuration file at /home/$USER/.config/MyApp/myguiapp.config
qt_config = QTConfigManager(self, 'MyApp', 'myguiapp') # self is owner of widgets
# Change the comment
qt_config._comment = "MyGUIApp: DO NOT HAND EDIT"  #  Appears at the top of the saved file
# Load list of items to save if not found (1st run)
qt_config.assign('ui_list', WDGT_LIST)
...
# Get GUI items from another form (MyForm2)
WDGT_LIST2 = ['cbCheckBox1', 'sbSpinBox2',...]
# Get GUI items from Myform2
qt_config.form2 = qt_config.save_qt(WDGT_LIST2, MyForm2) # This will be saved later when .save_config() is called
...
# Restore values to MyForm2
qt_config.restore_qt(qt_config.form2, MyForm2) # Make sure MyForm2 exists first
...
qt_config.save_config()

Footnotes

1. Any type from bool, str, bytes, int, float, complex, list, tuple, dict or set. ↩