1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
|
"""Object Utilities."""
class cached_property:
"""Cached property descriptor.
Caches the return value of the get method on first call.
Examples:
.. code-block:: python
@cached_property
def connection(self):
return Connection()
@connection.setter # Prepares stored value
def connection(self, value):
if value is None:
raise TypeError('Connection must be a connection')
return value
@connection.deleter
def connection(self, value):
# Additional action to do at del(self.attr)
if value is not None:
print('Connection {0!r} deleted'.format(value)
"""
def __init__(self, fget=None, fset=None, fdel=None, doc=None):
self.__get = fget
self.__set = fset
self.__del = fdel
self.__doc__ = doc or fget.__doc__
self.__name__ = fget.__name__
self.__module__ = fget.__module__
def __get__(self, obj, type=None):
if obj is None:
return self
try:
return obj.__dict__[self.__name__]
except KeyError:
value = obj.__dict__[self.__name__] = self.__get(obj)
return value
def __set__(self, obj, value):
if obj is None:
return self
if self.__set is not None:
value = self.__set(obj, value)
obj.__dict__[self.__name__] = value
def __delete__(self, obj, _sentinel=object()):
if obj is None:
return self
value = obj.__dict__.pop(self.__name__, _sentinel)
if self.__del is not None and value is not _sentinel:
self.__del(obj, value)
def setter(self, fset):
return self.__class__(self.__get, fset, self.__del)
def deleter(self, fdel):
return self.__class__(self.__get, self.__set, fdel)
|
