memcached.py 文件源码

def incr(self, key, delta=1, version=None):
        key = self.make_key(key, version=version)
        # memcached doesn't support a negative delta
        if delta < 0:
            return self._cache.decr(key, -delta)
        try:
            val = self._cache.incr(key, delta)

        # python-memcache responds to incr on non-existent keys by
        # raising a ValueError, pylibmc by raising a pylibmc.NotFound
        # and Cmemcache returns None. In all cases,
        # we should raise a ValueError though.
        except self.LibraryValueNotFoundException:
            val = None
        if val is None:
            raise ValueError("Key '%s' not found" % key)
        return val