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