terom@44: """
terom@44:     Miscellaneous utilities
terom@44: """
terom@44: 
terom@59: import functools
terom@23: 
terom@59: class LazyProperty (property) :
terom@12:     """
terom@59:         Lazy-loaded properties
terom@12:     """
terom@12: 
terom@59:     def __init__ (self, func) :
terom@59:         """
terom@59:             Initialize with no value
terom@59:         """
terom@12: 
terom@59:         super(LazyProperty, self).__init__(func)
terom@19: 
terom@59:         self.value = None
terom@26: 
terom@59:     def run (self) :
terom@59:         """
terom@59:             Run the background func and return the to-be-cached value
terom@59:         """
terom@28: 
terom@59:         return super(LazyProperty, self).__call__()
terom@59: 
terom@59:     def __call__ (self) :
terom@59:         """
terom@59:             Return the cached value if it exists, otherwise, call the func
terom@59:         """
terom@59: 
terom@59:         if not self.value :
terom@59:             # generate it
terom@59:             self.value = self.run()
terom@59: 
terom@59:         return self.value
terom@59: 
terom@59: class LazyIteratorProperty (LazyProperty) :
terom@59:     """
terom@59:         A lazy-loaded property that automatically converts an iterator/genexp into a list.
terom@59:     """
terom@59: 
terom@59:     def run (self) :
terom@59:         """
terom@59:             Wrap LazyProperty.run to return a list
terom@59:         """
terom@59: 
terom@59:         return list(super(LazyIteratorProperty, self).run())
terom@59: 
terom@59: lazy_load = LazyProperty
terom@59: lazy_load_iter = LazyIteratorProperty
terom@59: