python指定大小的字典实现，python指定字典,一段示例程序，从pyth

python指定大小的字典实现，python指定字典,一段示例程序，从pyth

一段示例程序，从python的默认dict继承，接口方法和默认的dict一模一样，单需要在构造函数中指定字典中允许的最多条目。

import timeclass SizedDict(dict):    ''' Sized dictionary without timeout. '''    def __init__(self, size=1000):        dict.__init__(self)        self._maxsize = size        self._stack = []    def __setitem__(self, name, value):        if len(self._stack) >= self._maxsize:            self.__delitem__(self._stack[0])            del self._stack[0]        self._stack.append(name)        return dict.__setitem__(self, name, value)    # Recommended but not required:    def get(self, name, default=None, do_set=False):        try:            return self.__getitem__(name)        except KeyError:            if default is not None:                if do_set:                    self.__setitem__(name, default)                return default            else:                raiseclass CacheDict(dict):    ''' A sized dictionary with a timeout (seconds) '''    def __init__(self, size=1000, timeout=None):        dict.__init__(self)        self._maxsize = size        self._stack = []        self._timeout = timeout    def __setitem__(self, name, value, timeout=None):        if len(self._stack) >= self._maxsize:            self.__delitem__(self._stack[0])            del self._stack[0]        if timeout is None:            timeout = self._timeout        if timeout is not None:            timeout = time.time() + timeout        self._stack.append(name)        dict.__setitem__(self, name, (value, timeout))    def get(self, name, default=None):        try:            focus = self.__getitem__(name)            if focus[1] is not None:                if focus[1] < time.time():                    self.__delitem__(name)                    self._stack.remove(name)                    raise KeyError            return focus[0]        except KeyError:            return default#sample usage:# d = SizedDict()# for i in xrange(10000): d[i] = 'test'# print len(d)