Why am I getting inconsistent exceptions in Python?

Question

In Python, I came across very strange behavior that is incompatible.

...
except IOError as msg:
    sys.exit("###ERROR IOError: %s" % (msg))

Normally this would get me a message like:

###ERROR IOError: [Errno 13] Permission denied: 'filename'

In the same cases, the above code gives me tupleinstead of the correct error message.

###ERROR IOError: (13, 'Permission denied')

This is very strange, because in all cases the exception comes from the same python method, codecs.open(...)

What makes me wonder about this is that if I delete the processing, the exception will reach the top levels with the correct text (full error message), always!

except IOError as msg:
    print(msg)
    raise msg

In the above example, the complete message will always be printed, for example IOError: [Errno 13] Permission denied: u'filename'.

Why this is happening and how I can prevent it, I do not want to provide users with incomplete error messages.

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, sys.exit(), print(msg) , sys.exit not.

Answer 1

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>>> print IOError(13, 'Permission denied')
[Errno 13] Permission denied
>>> print IOError((13, 'Permission denied'))
(13, 'Permission denied')

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Answer 2

Python 1.5 . , . .

, :

error = (13, 'Permision denied')

#more code

raise error

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raise IOError(error)

Answer 3

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