12.09.18 01:23, Victor Stinner пише:
> But then Petr Viktorin asked me to open a thread on python-dev to get
> a wider discussion. So here I am.
Thank you for opening this discussion Victor. I wanted to do it myself,
but you have wrote much better description of the problem. See also
related issues:
https://bugs.python.org/issue21861
https://bugs.python.org/issue22032 (solved)
https://bugs.python.org/issue22033 (solved)
https://bugs.python.org/issue27541 (solved)
https://bugs.python.org/issue28062
There were also attempts to change repr/str of types so that they return
just a FQN. It would help to solve the issue from Python side. This idea
was initially suggested by Guido, but later he changed his mind.
> The rationale for this change is to fix multiple issues:
>
> * C extensions use Py_TYPE(obj)->tp_name which returns a fully
> qualified name for C types, but the name (without the module) for
> Python name. Python modules use type(obj).__name__ which always return
> the short name.
Sometimes Python modules use FQN, but this is not common, and the code
is cumbersome. It is more common to use obj.__class__ instead of
type(obj), the difference is intentionally ignored.
> * currently, many C extensions truncate the type name: use "%.80s"
> instead of "%s" to format a type name
AFAIK the rationale of this in PyUnicode_FromFormat() is that if you
have corrupted type object, tp_name can point on arbitrary place in
memory, and an attempt to interpret it as null terminated string can
output a large amount of trash. It is better to get a truncated type
name in error message (names of real types usually are below that limit)
than get tons of trash or an error in attempt to format it.
> Maybe we can have "name: {0:t}, FQN: {0:T}".format(type(obj)). "t" for
> name and "T" for fully qualfied name. We would only have to modify
> type.__format__().
This will make the feature inconsistent in Python and C. In Python, the
argument is a type, in C it is an instance of the type. We need a way to
format a FQN in C for types themselves. It is less common case, but
using _PyType_FullName() for it is very non-convenient as you have shown
above.
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