When we define some members with PyMemberDef, we have to specify the flag for read-write or read-only. 

static PyMemberDef members[] = {
    {"name", T_OBJECT, offsetof(MyObject, name), 0, "Name object"},
    {NULL}  // Sentinel
};

For a newcomer, when you read the doc, you don't know the meaning of `0` and you want to know, of course you read the code and sometimes you can find READONLY or `0`.

I would like to add a new constant for `0` and name it `READWRITE`.

static PyMemberDef members[] = {
    {"name", T_OBJECT, offsetof(MyObject, name), READWRITE, "Name object"},
    {NULL}  // Sentinel
};