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Editing: lazy.py
from threading import RLock try: from UserDict import DictMixin except ImportError: from collections import Mapping as DictMixin # With lazy loading, we might end up with multiple threads triggering # it at the same time. We need a lock. _fill_lock = RLock() class LazyDict(DictMixin): """Dictionary populated on first use.""" data = None def __getitem__(self, key): if self.data is None: _fill_lock.acquire() try: if self.data is None: self._fill() finally: _fill_lock.release() return self.data[key.upper()] def __contains__(self, key): if self.data is None: _fill_lock.acquire() try: if self.data is None: self._fill() finally: _fill_lock.release() return key in self.data def __iter__(self): if self.data is None: _fill_lock.acquire() try: if self.data is None: self._fill() finally: _fill_lock.release() return iter(self.data) def __len__(self): if self.data is None: _fill_lock.acquire() try: if self.data is None: self._fill() finally: _fill_lock.release() return len(self.data) def keys(self): if self.data is None: _fill_lock.acquire() try: if self.data is None: self._fill() finally: _fill_lock.release() return self.data.keys() class LazyList(list): """List populated on first use.""" _props = [ '__str__', '__repr__', '__unicode__', '__hash__', '__sizeof__', '__cmp__', '__lt__', '__le__', '__eq__', '__ne__', '__gt__', '__ge__', 'append', 'count', 'index', 'extend', 'insert', 'pop', 'remove', 'reverse', 'sort', '__add__', '__radd__', '__iadd__', '__mul__', '__rmul__', '__imul__', '__contains__', '__len__', '__nonzero__', '__getitem__', '__setitem__', '__delitem__', '__iter__', '__reversed__', '__getslice__', '__setslice__', '__delslice__'] def __new__(cls, fill_iter=None): if fill_iter is None: return list() # We need a new class as we will be dynamically messing with its # methods. class LazyList(list): pass fill_iter = [fill_iter] def lazy(name): def _lazy(self, *args, **kw): _fill_lock.acquire() try: if len(fill_iter) > 0: list.extend(self, fill_iter.pop()) for method_name in cls._props: delattr(LazyList, method_name) finally: _fill_lock.release() return getattr(list, name)(self, *args, **kw) return _lazy for name in cls._props: setattr(LazyList, name, lazy(name)) new_list = LazyList() return new_list # Not all versions of Python declare the same magic methods. # Filter out properties that don't exist in this version of Python # from the list. LazyList._props = [prop for prop in LazyList._props if hasattr(list, prop)] class LazySet(set): """Set populated on first use.""" _props = ( '__str__', '__repr__', '__unicode__', '__hash__', '__sizeof__', '__cmp__', '__lt__', '__le__', '__eq__', '__ne__', '__gt__', '__ge__', '__contains__', '__len__', '__nonzero__', '__getitem__', '__setitem__', '__delitem__', '__iter__', '__sub__', '__and__', '__xor__', '__or__', '__rsub__', '__rand__', '__rxor__', '__ror__', '__isub__', '__iand__', '__ixor__', '__ior__', 'add', 'clear', 'copy', 'difference', 'difference_update', 'discard', 'intersection', 'intersection_update', 'isdisjoint', 'issubset', 'issuperset', 'pop', 'remove', 'symmetric_difference', 'symmetric_difference_update', 'union', 'update') def __new__(cls, fill_iter=None): if fill_iter is None: return set() class LazySet(set): pass fill_iter = [fill_iter] def lazy(name): def _lazy(self, *args, **kw): _fill_lock.acquire() try: if len(fill_iter) > 0: for i in fill_iter.pop(): set.add(self, i) for method_name in cls._props: delattr(LazySet, method_name) finally: _fill_lock.release() return getattr(set, name)(self, *args, **kw) return _lazy for name in cls._props: setattr(LazySet, name, lazy(name)) new_set = LazySet() return new_set # Not all versions of Python declare the same magic methods. # Filter out properties that don't exist in this version of Python # from the list. LazySet._props = [prop for prop in LazySet._props if hasattr(set, prop)]
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