pyndb 2.656

A way of saving data to a file with syntactic convenience

pyndb

pyndb, short for Python Node Database, is a pacakge which makes it easy to save data to a file while also providing syntactic convenience. It utilizes a Node structure which allows for easily retrieving nested objects. All data is wrapped inside of a custom Node object, and stored to file as nested dictionaries. It provides additional capabilities such as autosave, saving a dictionary to file, creating a file if none exists, and more. The original program was developed with the sole purpose of saving dictionaries to files, and was not released to the public.

Install

To install, you can either install via pip:
pip install pyndb
Or, you can download the package folder and run:
python -m pip install dist/*.whl

How values are represented

All keys in a dictionary managed by a PYNDatabase object will be represented as Node objects. Each Node object scans the dictionary it represents, and creates new Nodes for each key. This process repeats recursively. A Node object can also represent any other class, but you must then use the transform method - or replace the value with a dictionary - in order to create a subnode.

Creating a new database

To create a new database, first import the PYNDatabase object. Once you have done this, you can initialize it and then store it in a variable. A PYNDatabase object can be initialized with a filename (string), or a dictionary. You can also set the autosave flag. These values CAN be changed later, by changing PYNDatabase.<file | autosave>.

Saving

If a PYNDatabase object is initialized with a dictionary, it will update the original dictionary object as changes are made. Otherwise, you must call PYNDatabase.save() (unless autosave is set to True). The save method also has a file flag, which allows for easily saving to another file.

Retrieving values

Since values are stored as Node objects, object retrieval will look something like this:
PYNDatabase.Node.Node.val

val is a variable which contains the value of the Node, and is linked to the original dictionary object.

To retrieve a dynamic object, you can use the get method like this:
PYNDatabase.Node.get('name_of_node').Node.val

This way, you can avoid writing code like this:
eval(f'PYNDatabase.Node.{name_of_node}.Node.val')

Changing values

To change the value of a Node, you must use the set method from the parent Node. The set method uses the following arguments:
set(name, val, create_if_not_exist=True)

Sample usage would look something like this:
PYNDatabase.Node.set('name_of_node', new_value)

set will create new values if they don't exist, but this can be changed by setting create_if_not_exist to False. This way it will just raise a NameError.

Creating new values

To create a new subnode, you can use the create method. It uses the following arguments:
create(name, val={})
As you can see, the value is set to an empty dictionary by default, but can easily be changed by modifying the val flag, or using the set method.
If the name given is already in use, an AlreadyExists Exception will be raised.

Deleting values

To delete a Node, you can use the delete method. The only argument it takes is the name parameter.

The transform method

The transform method places the existing value of a Node into a dictionary under a user-defined key. The arguments for this method are shown below:
transform(name, new_name)

This method can be easily understood with the aid of a before and after diagram:

Before

None

After

{'new_name': None}

IDEs not playing nice

Some IDEs may throw errors saying that the PYNDatabase class does not have the attribute you requested. Technically, they're not wrong, as it hasn't been created yet. In PyCharm, the fix is simple: enter the context actions menu, and select "Mark all unresolved attributes of PYNDatabase as ignored." as shown in the image below:

Known limitations

• Nodes cannot contain special characters except for _ and -
• There is no good way to change the master value (setting PYNDatabase.fileObj does not modify the Nodes within the database, only the master value.)
  • To work around this, simply redeclare the variable your PYNDatabase is stored in with a dictionary, and set PYNDatabase.file to the filename.

Naming conventions

The proper (though not required) filename extension for a PYNDatabase is .pyndb

Fun fact: In earlier versions not released to the public, the project was named DataManager and did not use the Node structure. Thus the proper filename extension was .pydb. This is partially how the name pyndb came to be.