Eric V. Smith <e...@trueblade.com> added the comment:
This is because Exception does not define __format__, so object.__format__ is
being called. object.__format__ does not allow any format specifier to be used.
You get the same error for any object without its own __format__, when you
supply a format spec.
>>> 'okay {0:s}'.format(sys)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported format string passed to module.__format__
The reason this is enforced is because it allows an Execption.__format__ to be
added in the future, without worrying what existing format specifiers are being
used. We had a problem adding complex.__format__ because people had supplied
format specs when formatting complex numbers, assuming they acted like strings.
But now we've prevented this problem from happening in the future.
If you want to provide str formatting options to something like an exception,
you should force-convert it to a str first, using !s:
>>> 'okay {0!s:*^10}'.format(Exception('test'))
'okay ***test***'
----------
components: +Interpreter Core -ctypes
nosy: +eric.smith
resolution: -> not a bug
stage: -> resolved
status: open -> closed
type: -> behavior
_______________________________________
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue33848>
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