On 10/30/2018 1:12 AM, Serhiy Storchaka wrote:

29.10.18 23:17, MRAB пише:

1. If you're pickling, then saying "pickle" is more helpful.

2. In English the usual long form is "cannot". Error messages tend to avoid abbreviations, and also tend to have lowercase after the colon, e.g.:

     "ZeroDivisionError: division by zero"

     "ValueError: invalid literal for int() with base 10: 'foo'"

3. If it's failing on an object (singular), then it's clearer to say "object".

4. Articles tend to be omitted.

5. Error messages tend to have quotes around the type name.

Therefore, my preference is for:

     "cannot pickle 'XXX' object"

Thank you Matthew, I'll use your variant.

Will something change the fact that in all these cases the pickling will be failed not just for specific object, but for all instances of the specified type?

That's why I suggested "object of type 'XXX'", to leave the type in a more prominent position, as it is generally more important to the issue than the object.