pyparsing.py 文件源码

def __init__(self, size):
                self.not_in_cache = not_in_cache = object()

                cache = {}
                key_fifo = collections.deque([], size)

                def get(self, key):
                    return cache.get(key, not_in_cache)

                def set(self, key, value):
                    cache[key] = value
                    if len(cache) > size:
                        cache.pop(key_fifo.popleft(), None)
                    key_fifo.append(key)

                def clear(self):
                    cache.clear()
                    key_fifo.clear()

                self.get = types.MethodType(get, self)
                self.set = types.MethodType(set, self)
                self.clear = types.MethodType(clear, self)

    # argument cache for optimizing repeated calls when backtracking through recursive expressions