Coverage for sources/accretive/objects.py: 100%

1# vim: set filetype=python fileencoding=utf-8: 

2# -*- coding: utf-8 -*- 

3 

4#============================================================================# 

5# # 

6# Licensed under the Apache License, Version 2.0 (the "License"); # 

7# you may not use this file except in compliance with the License. # 

8# You may obtain a copy of the License at # 

9# # 

10# http://www.apache.org/licenses/LICENSE-2.0 # 

11# # 

12# Unless required by applicable law or agreed to in writing, software # 

13# distributed under the License is distributed on an "AS IS" BASIS, # 

14# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # 

15# See the License for the specific language governing permissions and # 

16# limitations under the License. # 

17# # 

18#============================================================================# 

19 

20 

21# pylint: disable=line-too-long 

22''' Accretive objects. 

23 

24Provides the base class for objects with accretive attributes. Once an 

25attribute is set on an instance, it cannot be reassigned or deleted. 

26 

27The implementation uses a special dictionary type for attribute storage that 

28enforces the accretive behavior. This makes it suitable as a base class for: 

29 

30* Configuration objects 

31* Plugin interfaces 

32* Immutable data containers 

33* Objects requiring attribute stability 

34 

35>>> from accretive import Object 

36>>> obj = Object( ) 

37>>> obj.x = 1 # Add new instance attribute 

38>>> obj.y = 2 # Add another instance attribute 

39>>> obj.x = 3 # Attempt modification 

40Traceback (most recent call last): 

41 ... 

42accretive.exceptions.AttributeImmutabilityError: Cannot reassign or delete existing attribute 'x'. 

43''' 

44# pylint: enable=line-too-long 

45 

46 

47from . import __ 

48from . import classes as _classes 

49 

50 

51class _Dictionary( 

52 __.CoreDictionary[ __.H, __.V ], metaclass = _classes.Class 

53): pass 

54 

55 

56class Object: 

57 ''' Accretive objects. ''' 

58 

59 __slots__ = ( '__dict__', ) 

60 

61 def __init__( self, *posargs: __.a.Any, **nomargs: __.a.Any ) -> None: 

62 super( ).__setattr__( '__dict__', _Dictionary( ) ) 

63 # Pass all arguments down MRO chain without consuming any. 

64 super( ).__init__( *posargs, **nomargs ) 

65 

66 def __repr__( self ) -> str: 

67 return "{fqname}( )".format( fqname = __.calculate_fqname( self ) ) 

68 

69 def __delattr__( self, name: str ) -> None: 

70 from .exceptions import AttributeImmutabilityError 

71 raise AttributeImmutabilityError( name ) 

72 

73 def __setattr__( self, name: str, value: __.a.Any ) -> None: 

74 if hasattr( self, name ): 

75 from .exceptions import AttributeImmutabilityError 

76 raise AttributeImmutabilityError( name ) 

77 super( ).__setattr__( name, value ) 

78 

79Object.__doc__ = __.generate_docstring( 

80 Object, 'instance attributes accretion' )