[libvirt] [PATCH v2] python: add virDomainGetCPUStats python binding API

[Guannan Ren]

On 03/21/2012 09:23 PM, Eric Blake wrote:
> On 03/21/2012 07:22 AM, Guannan Ren wrote:
>> On 03/21/2012 08:07 PM, Eric Blake wrote:
>>> Maybe we need a wrapper:
>>>
>>> int libvirt_boolUnwrap(PyObject *obj, bool *value) {
>>>       int ret = PyObject_IsTrue(obj);
>>>       if (ret<   0)
>>>           return ret;
>>>       *value = ret>   0;
>>>       return 0;
>>> }
>>>
>>> and then callers become:
>>>
>>>       if (libvirt_boolUnwrap(value,&temp->value.b)<   0)
>>>           goto cleanup;
>>>
>>       The libvirt_boolUnwrap is okay to be flexible like this, we still need
>>     the caller to check whether or not the value given from user python code
>>     is boolean argument, we need to do the data type checking in python C
>> API
>>     before invoking the wrapper.
> But that's my point - the wrapper should be doing the type checking
> (PyObject_IsTrue already _does_ some type checking - that's why it can
> fail with -1 with an already decent python exception created).  Callers
> shouldn't have to duplicate the work which can be done in just one
> place, but instead just pass in an object of unknown type and let the
> wrapper do the work of both type validation and conversion if the type
> was usable as a boolean.
>
      I get your points,  sorry I don't express my idea clearly.
      According to my experience, for PyObject_IsTrue, all of non-null 
objects
      belongs to True,  null objects like {}, ""(str) ,None, False
      counts as False,  it's good way to work with Pybool_check to ensure
      the type of value given by upper python code is right type.  The 
wrapper
      should do the job.