1"""Module for wrapping an array without being an array. 

2 

3This can be desirable because we would like atoms.cell to be like an array, 

4but we don't like atoms.positions @ atoms.cell to also be a cell, and as far 

5as I/we know, it's not possible to subclass array without that kind of thing 

6happening. 

7 

8For most methods and attributes we can just bind the name as a property: 

9 

10 @property 

11 def reshape(self): 

12 return np.asarray(self).reshape 

13 

14For 'in-place' operations like += we need to make sure to return self 

15rather than the array though: 

16 

17 def __iadd__(self, other): 

18 np.asarray(self).__iadd__(other) 

19 return self 

20 

21This module provides the @arraylike decorator which does these things 

22for all the interesting ndarray methods. 

23""" 

24 

25 

26from functools import update_wrapper 

27import numpy as np 

28 

29 

30inplace_methods = ['__iadd__', '__imul__', '__ipow__', '__isub__', 

31 '__itruediv__', '__imatmul__'] 

32 

33forward_methods = ['__abs__', '__add__', '__contains__', '__eq__', 

34 '__ge__', '__getitem__', '__gt__', '__hash__', 

35 '__iter__', '__le__', '__len__', '__lt__', 

36 '__mul__', '__ne__', '__neg__', '__pos__', 

37 '__pow__', '__radd__', '__rmul__', '__rpow__', 

38 '__rsub__', '__rtruediv__', '__setitem__', 

39 '__sub__', '__truediv__'] 

40 

41default_methods = ['__eq__', '__le__', '__lt__', '__ge__', 

42 '__gt__', '__ne__', '__hash__'] 

43 

44if hasattr(np.ndarray, '__matmul__'): 

45 forward_methods += ['__matmul__', '__rmatmul__'] 

46 

47 

48def forward_inplace_call(name): 

49 arraymeth = getattr(np.ndarray, name) 

50 

51 def f(self, obj): 

52 a = self.__array__() 

53 arraymeth(a, obj) 

54 return self 

55 

56 update_wrapper(f, arraymeth) 

57 return f 

58 

59 

60def wrap_array_attribute(name): 

61 wrappee = getattr(np.ndarray, name) 

62 if wrappee is None: # For example, __hash__ is None 

63 assert name == '__hash__' 

64 return None 

65 

66 def attr(self): 

67 array = np.asarray(self) 

68 return getattr(array, name) 

69 

70 update_wrapper(attr, wrappee) 

71 

72 # We don't want to encourage too liberal use of the numpy methods, 

73 # nor do we want the web docs to explode with numpy docstrings or 

74 # break our own doctests. 

75 # 

76 # Therefore we cheat and remove the docstring: 

77 attr.__doc__ = None 

78 return property(attr) 

79 

80 

81def arraylike(cls): 

82 """Decorator for being like an array without being an array. 

83 

84 Poke decorators onto cls so that getting an attribute 

85 really gets that attribute from the wrapped ndarray. 

86 

87 Exceptions are made for in-place methods like +=, *=, etc. 

88 These must return self since otherwise myobj += 1 would 

89 magically turn into an ndarray.""" 

90 for name in inplace_methods: 

91 if hasattr(np.ndarray, name) and not hasattr(cls, name): 

92 meth = forward_inplace_call(name) 

93 setattr(cls, name, meth) 

94 

95 allnames = [name for name in dir(np.ndarray) if not name.startswith('_')] 

96 for name in forward_methods + allnames: 

97 if hasattr(cls, name) and name not in default_methods: 

98 continue # Was overridden -- or there's a conflict. 

99 

100 prop = wrap_array_attribute(name) 

101 setattr(cls, name, prop) 

102 return cls