python exception message formatting [closed]

Question

Question: Why don't I get an exception message when formatting the message with %s but I do with format?

Fails:

>>> Exception('foo %s', 'bar').message
''

Works:

>>> Exception('foo {}'.format('bar')).message
'foo bar'

Any explanation why it fails on %s?

Answer 1

Your syntax for the %-substitution in Exception is incorrect. You need to use % to specify the replacement string:

>>> Exception('foo %s' % 'bar').message
'foo bar'