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  1. from collections import defaultdict
  2.  
  3. class IndexedSet:
  4. 	def __init__(self):
  5. 		self._elements = set()
  6. 		self._indices = set()
  7.  
  8. 	def add(self, element):
  9. 		self._elements.add(element)
  10. 		for index in self._indices:
  11. 			index.add(element)
  12.  
  13. 	def remove(self, element):
  14. 		self._elements.remove(element)
  15. 		for index in self._indices:
  16. 			index.remove(element)
  17.  
  18. 	def index(self, key):
  19. 		index = Index(key)
  20. 		for element in self._elements:
  21. 			index.add(element)
  22. 		self._indices.add(index)
  23. 		return index
  24.  
  25. class Index:
  26. 	def __init__(self, key):
  27. 		self._key = key
  28. 		self._elements = defaultdict(set)
  29.  
  30. 	def add(self, element):
  31. 		self._elements[self._key(element)].add(element)
  32.  
  33. 	def remove(self, element):
  34. 		self._elements[self._key(element)].remove(element)
  35. 		if len(self._elements[self._key(element)]) == 0:
  36. 			del self._elements[self._key(element)]
  37.  
  38. 	def find(self, key):
  39. 		return self._elements[key]
  40.  
  41. # example:
  42. from operator import attrgetter
  43.  
  44. class User:
  45. 	def __init__(self, id, email_address, password_hash):
  46. 		self.id = id
  47. 		self.email_address = email_address
  48. 		self.password_hash = password_hash
  49.  
  50. 	@property
  51. 	def _tuple(self):
  52. 		return self.id, self.email_address, self.password_hash
  53.  
  54. 	def __eq__(self, other):
  55. 		return isinstance(other, User) and self._tuple == other._tuple
  56.  
  57. 	def __hash__(self):
  58. 		return hash(self._tuple)
  59.  
  60. users = IndexedSet()
  61. id_index = users.index(attrgetter('id'))
  62. email_address_index = users.index(attrgetter('email_address'))
  63. users.add(User(1, 'rightfold@gmail.com', b'abcd'))
  64. users.add(User(2, 'henk@example.com', b'defg'))
  65. print(id_index.find(1))
  66. print(id_index.find(2))
  67. print(id_index.find(3))
  68. print(email_address_index.find('rightfold@gmail.com'))
  69. print(email_address_index.find('henk@example.com'))
  70. print(email_address_index.find('foo@bar.baz'))
Success #stdin #stdout 0.03s 9008KB
comments (?)
stdin 
Standard input is empty
stdout 
{<__main__.User object at 0xb7470aec>}
{<__main__.User object at 0xb7470b2c>}
set()
{<__main__.User object at 0xb7470aec>}
{<__main__.User object at 0xb7470b2c>}
set()
https://ideone.com/mZjVgt
language:
Python 3 (python  3.9.5)
created:
9 years ago
visibility:
secret

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