cache_context.py

class HumbleCachedContext:
    """Only pulls what it needs, and never pulls twice
    """

    def __init__(self, **context_items):
        self.get_functions = {}
        for key, value in context_items:
            self.add(key, value)

    def cache_key(self, key):
        return '_' + key

    def function_key(self, key):
        return 'get_' + key

    def set(self, key, value):
        if hasattr(value, '__call__'):
            function_key = self.function_key(key)
            self.get_functions[function_key] = value
        else:
            cache_key = self.cache_key(key)
            setattr(self, cache_key, value)

    def get(self, key, default_getter=None):
        cache_key = self.cache_key(key)
        if hasattr(self, cache_key):
            return getattr(self, cache_key)
        else:
            function_key = self.function_key(key)
            if function_key in self.get_functions:
                value = self.get_functions[function_key]()
                setattr(self, cache_key, value)
                return value
            elif default_getter:
                value = default_getter()
                setattr(self, cache_key, value)
                return value
            else:
                raise KeyError

    def __getattr__(self, key):
        return self.get(key)