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cpython/Doc/library/email.errors.rst
R David Murray 29d1bc0842 #24277: The new email API is no longer provisional.
This is a wholesale reorganization and editing of the email documentation to
make the new API the standard one, and the old API the 'legacy' one.  The
default is still the compat32 policy, for backward compatibility.  We will
change that eventually.
2016-09-07 21:15:59 -04:00

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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
enocded 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
enocded bytes, characters outside the base64 alphebet were encountered.
The characters are ignored, but the resulting decoded bytes may be invalid.