Coverage for backpack/__init__.py: 100%

1''' Utilities for AWS Panorama application development. ''' 

2 

3__version__ = '0.3.2' 

4__author__ = 'Janos Tolgyesi' 

5 

6import functools 

7 

8def lazy_property(func): 

9 ''' Caches the return value of a function, and turns it into a property. 

10 

11 Intended to be used as a function decorator:: 

12 

13 >>> class Foo: 

14 >>> @lazy_property 

15 >>> def bar(self): 

16 >>> print('expensive calculation') 

17 >>> return 'bar' 

18 >>> foo = Foo() 

19 >>> foo.bar() 

20 expensive calculation 

21 'bar' 

22 >>> foo.bar() 

23 'bar' 

24 ''' 

25 attrib_name = '_' + func.__name__ 

26 @property 

27 @functools.wraps(func) 

28 def lazy_wrapper(instance, *args, **kwargs): 

29 if hasattr(instance, attrib_name): 

30 return getattr(instance, attrib_name) 

31 value = func(instance, *args, **kwargs) 

32 object.__setattr__(instance, attrib_name, value) 

33 return value 

34 return lazy_wrapper