Lazy dict

lazy_dict.py

# Wrote this before realizing django.utils.functional.lazy existed.

class LazyDict(dict):
    """
    Loads data lazily.
    """
    def __init__(self, loader, *args, **kwargs):
        self._data_loaded = False
        self.loader = loader
        super(LazyDict, self).__init__(*args, **kwargs)

    def load_data(func):
        def _dec(*args, **kwargs):
            self = args[0]
            if not self._data_loaded:
                self._load_data()
            return func(*args, **kwargs)
        return _dec

    @load_data
    def __getitem__(self, k):
        return super(LazyDict, self).__getitem__(k)

    @load_data
    def __setitem__(self, k, v):
        return super(LazyDict, self).__setitem__(k, v)

    @load_data
    def __contains__(self, k):
        return super(LazyDict, self).__contains__(k)

    @load_data
    def __delitem__(self, k):
        return super(LazyDict, self).__delitem__(k)

    def _load_data(self):
        data = self.loader()
        for k, v in data.items():
            super(LazyDict, self).__setitem__(k, v)
        self._data_loaded = True