CascaDict - cascading dictionary for Python

This little class aims to solve just another almost nonexistent problem - handling of cascading properties. To describe it simply, CascaDict implements something like class inheritance, but on dictionary-key level. See the examples:

from cascadict import CascaDict

fruit_properties = CascaDict({'type':'fruit', 'taste':'sweet', 'color':"I don't have any color, I'm an abstract concept!"})
blueberry = fruit_properties.cascade({'name': 'blueberry', 'color':'blue'})

print(blueberry['color'])
print(blueberry['taste'])

blue
sweet

Internally, it's not just copy and append, one can also access all the cascaded values:

print(blueberry.get_cascaded('color'))

['blue', "I don't have any color, I'm an abstract concept!"]

Cascaded ancestors are referenced, not copied:

fruit_properties['taste'] = 'bittersweet'
blueberry['taste']

'bittersweet'

CascaDicts can be nested, and any dict element put into CascaDict is also nested as CascaDict:

fruit_properties['classification'] = {'kingdom': 'Plantae',}
blueberry['classification'] = {'Order': 'Ericales', 'Family': 'Ericaceae', 'Genus': 'Vaccinium', 'Section': 'Cyanococcus'}

blueberry['classification']['kingdom']

'Plantae'

CascaDicts are of course iterable...

for key, value in blueberry.items():
	print(key,value)

('color', 'blue')
('name', 'blueberry')
('classification', <{'Section': 'Cyanococcus', 'Genus': 'Vaccinium', 'Order': 'Ericales', 'Family': 'Ericaceae'}, Ancestor: <{}, Ancestor: <{'kingdom': 'Plantae'}, Ancestor: None>>>)
('taste', 'bittersweet')
('type', 'fruit')

... and picklable

import pickle
blueberry_jam = pickle.loads(pickle.dumps(blueberry))
for key, value in blueberry_jam.items():
	print(key,value)

('color', 'blue')
('name', 'blueberry')
('classification', <{'Section': 'Cyanococcus', 'Genus': 'Vaccinium', 'Order': 'Ericales', 'Family': 'Ericaceae'}, Ancestor: <{}, Ancestor: <{'kingdom': 'Plantae'}, Ancestor: None>>>)
('taste', 'bittersweet')
('type', 'fruit')

If needed, CascaDict can be "flattened" into normal (nested) dict:

blueberry.copy_flat()

{'classification': {'Family': 'Ericaceae',
  'Genus': 'Vaccinium',
  'Order': 'Ericales',
  'Section': 'Cyanococcus',
  'kingdom': 'Plantae'},
 'color': 'blue',
 'name': 'blueberry',
 'taste': 'bittersweet',
 'type': 'fruit'}

Or only the top (final) level of CascaDict, without any ancestor properties, can be copied:

blueberry.copy_flat(level='skim')

{'classification': {'Family': 'Ericaceae',
  'Genus': 'Vaccinium',
  'Order': 'Ericales',
  'Section': 'Cyanococcus'},
 'color': 'blue',
 'name': 'blueberry'}

Combined with (e.g.) yaml, it makes any configuration processing a breeze:

import yaml

config = '''
defaults:
	port: 5556
	login_required: True
	logging: 
		level: DEBUG
		handler: stream
		
process_1:
	max_runtime: 100
	login_required: False
	logging:
		handler: file
	
process_2:
	port: 6005
	halt_on_error: True
	logging:
		level: ERROR

'''

raw_config = yaml.load(config)
defaults = CascaDict(raw_config.pop('defaults'))
properties = {} #no dict comprehension, remember Python 2.7 folk
for k,v in raw_config.items():
	properties[k] = CascaDict(v, ancestor=defaults)
	
for k,v in properties.items():
	print("{0}: {1}".format(k, v.copy_flat()))

process_2: {'login_required': True, 'logging': {'handler': 'stream', 'level': 'ERROR'}, 'port': 6005, 'halt_on_error': True}
process_1: {'logging': {'handler': 'file', 'level': 'DEBUG'}, 'login_required': False, 'max_runtime': 100, 'port': 5556}

See full documentation on ReadTheDocs.

That's it

This whole thing is just one small file, works in both Python 2.7 and 3.x and is released under MIT License. Now, cascade!

nicodemus26/cascadict

CascaDict - cascading dictionary for Python

That's it