cpython/Doc/library/email.errors.rst

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:mod:`email.errors`: Exception and Defect classes
-------------------------------------------------
.. module:: email.errors
:synopsis: The exception classes used by the email package.
The following exception classes are defined in the :mod:`email.errors` module:
.. exception:: MessageError()
This is the base class for all exceptions that the :mod:`email` package can
raise. It is derived from the standard :exc:`Exception` class and defines no
additional methods.
.. exception:: MessageParseError()
This is the base class for exceptions raised by the :class:`~email.parser.Parser`
class. It is derived from :exc:`MessageError`.
.. exception:: HeaderParseError()
Raised under some error conditions when parsing the :rfc:`2822` headers of a
message, this class is derived from :exc:`MessageParseError`. It can be raised
from the :meth:`Parser.parse` or :meth:`Parser.parsestr` methods.
Situations where it can be raised include finding an envelope header after the
first :rfc:`2822` header of the message, finding a continuation line before the
first :rfc:`2822` header is found, or finding a line in the headers which is
neither a header or a continuation line.
.. exception:: BoundaryError()
Raised under some error conditions when parsing the :rfc:`2822` headers of a
message, this class is derived from :exc:`MessageParseError`. It can be raised
from the :meth:`Parser.parse` or :meth:`Parser.parsestr` methods.
Situations where it can be raised include not being able to find the starting or
terminating boundary in a :mimetype:`multipart/\*` message when strict parsing
is used.
.. exception:: MultipartConversionError()
Raised when a payload is added to a :class:`Message` object using
:meth:`add_payload`, but the payload is already a scalar and the message's
:mailheader:`Content-Type` main type is not either :mimetype:`multipart` or
missing. :exc:`MultipartConversionError` multiply inherits from
:exc:`MessageError` and the built-in :exc:`TypeError`.
Since :meth:`Message.add_payload` is deprecated, this exception is rarely raised
in practice. However the exception may also be raised if the :meth:`attach`
method is called on an instance of a class derived from
:class:`~email.mime.nonmultipart.MIMENonMultipart` (e.g.
:class:`~email.mime.image.MIMEImage`).
Here's the list of the defects that the :class:`~email.mime.parser.FeedParser`
can find while parsing messages. Note that the defects are added to the message
where the problem was found, so for example, if a message nested inside a
:mimetype:`multipart/alternative` had a malformed header, that nested message
object would have a defect, but the containing messages would not.
All defect classes are subclassed from :class:`email.errors.MessageDefect`, but
this class is *not* an exception!
.. versionadded:: 2.4
All the defect classes were added.
* :class:`NoBoundaryInMultipartDefect` -- A message claimed to be a multipart,
but had no :mimetype:`boundary` parameter.
* :class:`StartBoundaryNotFoundDefect` -- The start boundary claimed in the
:mailheader:`Content-Type` header was never found.
* :class:`FirstHeaderLineIsContinuationDefect` -- The message had a continuation
line as its first header line.
* :class:`MisplacedEnvelopeHeaderDefect` - A "Unix From" header was found in the
middle of a header block.
* :class:`MalformedHeaderDefect` -- A header was found that was missing a colon,
or was otherwise malformed.
* :class:`MultipartInvariantViolationDefect` -- A message claimed to be a
:mimetype:`multipart`, but no subparts were found. Note that when a message has
this defect, its :meth:`is_multipart` method may return false even though its
content type claims to be :mimetype:`multipart`.