PEP 737 – Unify type name formatting

[vstinner (Victor Stinner)]

I prepared a PEP 737 change to address comments.

Changes:

• Add %N and %#N formats.
• The %T and %#T formats now expect an object instead of a type.
• Exchange %T and %#T formats: %T now formats the fully qualified name.
• Recommend using the type fully qualified name in error messages and in __repr__() methods when writing new code.

@eric.snow

If the goal is consistency, shouldn’t we then normalize for __main__, either updating pdb/traceback to show it or updating the rest to not?

If __main__ is omitted, is there a risk to have other types with the same short name in other modules? Does "__main__." makes the type unambiguous?

@Jelle

I could get behind __full_qualname__.

Another attribute name which was not proposed so far: type.__fullname__

@ronaldoussoren

What’s the preferred format to use when formatting errors? I’d expect that using the fully qualified name is often the most useful, maybe switch around the two options, e.g. %T for the fully qualified name and %#T for the short name.

I updated the PEP to recommend using the fully qualified name when writing new code. I modified %T format to use the fully qualified name.

@encukou

Is this a recommendation for new (or touched) code, or an invitation to change all/most occurences of %.100s?

In my update, I made it explicit: I would like to modify the whole stdlib to no longer truncate type names. Type names longer than 100 characters are unlikely, so this specific change should not affect anyway in practice.

@encukou

Which format parser are you talking about here?

I’m thinking about Python/formatter_unicode.c which uses a regular specification for format() string. The grammar of this specification can be found in the Python documentation.