How to catch a usefull error message ?

[Vincent Vande Vyvre]

Le 23/04/19 à 19:27, MRAB a écrit :
> On 2019-04-23 10:56, Vincent Vande Vyvre wrote:
>> Hi,
>>
>> In a CPython lib I have an _init() method wich take one argument, a file
>> name.
>>
>>       char *fname;
>>
>>       if (!PyArg_ParseTuple(args, "s", &fname))
>>           return NULL;
>>
>> So, if I instanciate my object with a bad argument I've a good error
>> message:
>>
>> tif = ImgProc(123)
>> TypeError: argument 1 must be str, not int
>> (followed by the traceback)
>>
>> But if I do:
>> try:
>>       tif = ImgProc(123)
>> except Exception as why:
>>       print("Error:", why)
>>
>> I get just:
>>
>> Error: <class '_liboqapy.ImgProc'> returned a result with an error set
>>
>> Without traceback. That's not very usefull.
>>
>> I prefer to keep the instanciation of this object into a try-except bloc
>> but how to read the error message ?
>>
> Have a look ta the 'traceback' module.
> Example:
>
> import traceback
>
> try:
>     1/0
> except Exception as ex:
>     print('Error:', ex)
>     traceback.print_exc()

     try:
         tif = ImgProc(123)
     except Exception as why:
         traceback.print_exc()
     print("always alive !")

TypeError: argument 1 must be str, not int

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
   File "/home/vincent/oqapy-3/trunk/filters/lenscorrection.py", line 
56, in process_on_preview
     tif = ImgProc(123)
SystemError: <class '_liboqapy.ImgProc'> returned a result with an error set
always alive !
-----------------------------------------------------------------------------

This is better of nothing and the try-except works.

Vincent