cython中的类变量和实例变量

Question

我正在阅读cython文档，并对出现在以下代码中的_c_queue和self._c_queue感到困惑。类变量_c_queue是否起任何作用？以下代码来自https://cython.readthedocs.io/en/latest/src/tutorial/clibraries.html

# distutils: sources = c-algorithms/src/queue.c
# distutils: include_dirs = c-algorithms/src/

cimport cqueue

cdef class Queue:
    cdef cqueue.Queue* _c_queue
    def __cinit__(self):
        self._c_queue = cqueue.queue_new()
        if self._c_queue is NULL:
            raise MemoryError()

    def __dealloc__(self):
        if self._c_queue is not NULL:
            cqueue.queue_free(self._c_queue)