On 13 Sep 2018, at 2:33, Victor Stinner wrote:
Hi,
For the type name, sometimes, we only get a type (not an instance),
and we want to format its FQN. IMHO we need to provide ways to format
the FQN of a type for *types* and for *instances*. Here is my
proposal:
* Add !t conversion to format string
* Add ":T" format to type.__format__()
* Add "%t" and "%T" formatters to PyUnicode_FromUnicodeV()
As far as I can remember, the distinction between lowercase and
uppercase format letter for PyUnicode_FromUnicodeV() and friends was:
lowercase letters are for formatting C types (like `char *` etc.) and
uppercase formatting letters are for Python types (i.e. the C type is
`PyObject *`). IMHO we should keep that distinction.
* Add a read-only type.__fqn__ property
I like that.
# Python: "!t" for instance
raise TypeError(f"must be str, not {obj!t}")
/* C: "%t" for instance */
PyErr_Format(PyExc_TypeError, "must be str, not %t", obj);
/* C: "%T" for type */
PyErr_Format(PyExc_TypeError, "must be str, not %T", mytype);
# Python: ":T" for type
raise TypeError(f"must be str, not {mytype!T}")
We could solve the problem with instances and classes by adding two new
! operators to str.format/f-strings and making them chainable. The !t
operator would get the class of the argument and the !c operator would
require a class argument and would convert it to its name (which is
obj.__module__ + "." + obj.__qualname__ (or only obj.__qualname__ for
builtin types)). So:
>>> import pathlib
>>> p = pathlib.Path("spam.py")
>>> print(f"{pathlib.Path}")
<class 'pathlib.Path'>
>>> print(f"{pathlib.Path!c}")
pathlib.Path
>>> print(f"{pathlib.Path!c!r}")
'pathlib.Path'
>>> print(f"{p!t}")
<class 'pathlib.Path'>
>>> print(f"{p!t!c}")
pathlib.Path
>>> print(f"{p!c}")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: object is not a class
This would also give us:
>>> print(f"{p!s!r}")
'spam.py'
Which is different from:
>>> print(f"{p}")
spam.py
>>> print(f"{p!r}")
PosixPath('spam.py')
Open question: Should we also add "%t" and "%T" formatters to the str
% args operator at the Python level?
I have a proof-of-concept implementation:
https://github.com/python/cpython/pull/9251
Victor
Servus,
Walter
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
https://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
