ys

Special dicts

To install: pip install ys

Overview

The ys package provides specialized dictionary classes that extend the functionality of Python's standard dict and collections.defaultdict. These classes include:

• keydefaultdict: A defaultdict variant where the default value for a missing key is generated dynamically based on the key itself.
• DictDefaultDict: A dictionary that provides default values for missing keys based on a predefined dictionary of key-value pairs.
• KeyPathDict: An advanced dictionary allowing access and modification of nested dictionary values using a key path (a dot-separated string or a list of keys).

Features

keydefaultdict

This class behaves like collections.defaultdict but allows the default factory function to receive the missing key as an argument. This is useful when the default value for each key needs to be determined dynamically.

DictDefaultDict

This dictionary class is initialized with another dictionary that specifies default values for certain keys. When accessing a key that does not exist in the DictDefaultDict, it will return the default value from the provided default dictionary if available.

KeyPathDict

This dictionary class supports accessing and setting values through a key path. A key path can be a dot-separated string or a list of nested keys, allowing for deep access into nested dictionaries. This feature is particularly useful for dealing with complex, nested data structures.

Usage Examples

Using keydefaultdict

from ys import keydefaultdict

def generate_default(key):
    return len(key)

kd = keydefaultdict(generate_default)
print(kd['hello'])  # Outputs 5, as the default factory uses the length of the key

Using DictDefaultDict

from ys import DictDefaultDict

defaults = {'missing': 'default value', 'another': 42}
dd = DictDefaultDict(defaults)
print(dd['missing'])  # Outputs 'default value'
print(dd['not_there'])  # Outputs KeyError as 'not_there' is not a predefined default

Using KeyPathDict

from ys import KeyPathDict

data = {
    'user': {
        'name': 'John Doe',
        'address': {
            'street': '123 Elm St',
            'city': 'Somewhere'
        }
    }
}
kpd = KeyPathDict(data)
print(kpd['user.address.street'])  # Outputs '123 Elm St'
kpd['user.address.zip_code'] = '12345'  # Adds a new nested key
print(kpd['user.address'])  # Outputs {'street': '123 Elm St', 'city': 'Somewhere', 'zip_code': '12345'}

These specialized dictionaries provide enhanced flexibility and functionality for handling complex data structures and dynamic default values in Python applications.