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:mod:`email.errors`: Exception and Defect classes

kbe/src/lib/python/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.

Source code: :source:Lib/email/errors.py

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. This class is also used internally by the parser used by :mod:~email.headerregistry.

.. exception:: HeaderParseError()

Raised under some error conditions when parsing the :rfc:5322 headers of a message, this class is derived from :exc:MessageParseError. The :meth:~email.message.EmailMessage.set_boundary method will raise this error if the content type is unknown when the method is called. :class:~email.header.Header may raise this error for certain base64 decoding errors, and when an attempt is made to create a header that appears to contain an embedded header (that is, there is what is supposed to be a continuation line that has no leading whitespace and looks like a header).

.. exception:: BoundaryError()

Deprecated and no longer used.

.. exception:: MultipartConversionError()

Raised when a payload is added to a :class:~email.message.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:~email.message.Message.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 is the list of the defects that the :class:~email.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.

  • :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:CloseBoundaryNotFoundDefect -- A start boundary was found, but no corresponding close boundary was ever found.

    .. versionadded:: 3.3

  • :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:MissingHeaderBodySeparatorDefect - A line was found while parsing headers that had no leading white space but contained no ':'. Parsing continues assuming that the line represents the first line of the body.

    .. versionadded:: 3.3

  • :class:MalformedHeaderDefect -- A header was found that was missing a colon, or was otherwise malformed.

    .. deprecated:: 3.3 This defect has not been used for several Python versions.

  • :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:~email.message.Message.is_multipart method may return false even though its content type claims to be :mimetype:multipart.

  • :class:InvalidBase64PaddingDefect -- When decoding a block of base64 encoded bytes, the padding was not correct. Enough padding is added to perform the decode, but the resulting decoded bytes may be invalid.

  • :class:InvalidBase64CharactersDefect -- When decoding a block of base64 encoded bytes, characters outside the base64 alphabet were encountered. The characters are ignored, but the resulting decoded bytes may be invalid.

  • :class:InvalidBase64LengthDefect -- When decoding a block of base64 encoded bytes, the number of non-padding base64 characters was invalid (1 more than a multiple of 4). The encoded block was kept as-is.