lazy.py
62 lines
| 1.5 KiB
| text/x-python
|
PythonLexer
| r3475 | class _Missing(object): | |||
| def __repr__(self): | ||||
| return 'no value' | ||||
| def __reduce__(self): | ||||
| return '_missing' | ||||
| _missing = _Missing() | ||||
| r2007 | class LazyProperty(object): | |||
| """ | ||||
| Decorator for easier creation of ``property`` from potentially expensive to | ||||
| calculate attribute of the class. | ||||
| Usage:: | ||||
| class Foo(object): | ||||
| @LazyProperty | ||||
| def bar(self): | ||||
| print 'Calculating self._bar' | ||||
| return 42 | ||||
| Taken from http://blog.pythonisito.com/2008/08/lazy-descriptors.html and | ||||
| used widely. | ||||
| """ | ||||
| def __init__(self, func): | ||||
| self._func = func | ||||
| r2494 | self.__module__ = func.__module__ | |||
| r2007 | self.__name__ = func.__name__ | |||
| self.__doc__ = func.__doc__ | ||||
| def __get__(self, obj, klass=None): | ||||
| if obj is None: | ||||
| r2494 | return self | |||
| r3475 | value = obj.__dict__.get(self.__name__, _missing) | |||
| if value is _missing: | ||||
| value = self._func(obj) | ||||
| obj.__dict__[self.__name__] = value | ||||
| return value | ||||
| r3050 | ||||
| import threading | ||||
| class ThreadLocalLazyProperty(LazyProperty): | ||||
| """ | ||||
| Same as above but uses thread local dict for cache storage. | ||||
| """ | ||||
| def __get__(self, obj, klass=None): | ||||
| if obj is None: | ||||
| return self | ||||
| if not hasattr(obj, '__tl_dict__'): | ||||
| obj.__tl_dict__ = threading.local().__dict__ | ||||
| r3475 | value = obj.__tl_dict__.get(self.__name__, _missing) | |||
| if value is _missing: | ||||
| value = self._func(obj) | ||||
| obj.__tl_dict__[self.__name__] = value | ||||
| return value | ||||
