/Doc/library/email.errors.rst

 1:mod:`email`: Exception and Defect classes
 2------------------------------------------
 3
 4.. module:: email.errors
 5   :synopsis: The exception classes used by the email package.
 6
 7
 8The following exception classes are defined in the :mod:`email.errors` module:
 9
10
11.. exception:: MessageError()
12
13   This is the base class for all exceptions that the :mod:`email` package can
14   raise.  It is derived from the standard :exc:`Exception` class and defines no
15   additional methods.
16
17
18.. exception:: MessageParseError()
19
20   This is the base class for exceptions thrown by the :class:`~email.parser.Parser`
21   class.  It is derived from :exc:`MessageError`.
22
23
24.. exception:: HeaderParseError()
25
26   Raised under some error conditions when parsing the :rfc:`2822` headers of a
27   message, this class is derived from :exc:`MessageParseError`. It can be raised
28   from the :meth:`Parser.parse` or :meth:`Parser.parsestr` methods.
29
30   Situations where it can be raised include finding an envelope header after the
31   first :rfc:`2822` header of the message, finding a continuation line before the
32   first :rfc:`2822` header is found, or finding a line in the headers which is
33   neither a header or a continuation line.
34
35
36.. exception:: BoundaryError()
37
38   Raised under some error conditions when parsing the :rfc:`2822` headers of a
39   message, this class is derived from :exc:`MessageParseError`. It can be raised
40   from the :meth:`Parser.parse` or :meth:`Parser.parsestr` methods.
41
42   Situations where it can be raised include not being able to find the starting or
43   terminating boundary in a :mimetype:`multipart/\*` message when strict parsing
44   is used.
45
46
47.. exception:: MultipartConversionError()
48
49   Raised when a payload is added to a :class:`Message` object using
50   :meth:`add_payload`, but the payload is already a scalar and the message's
51   :mailheader:`Content-Type` main type is not either :mimetype:`multipart` or
52   missing.  :exc:`MultipartConversionError` multiply inherits from
53   :exc:`MessageError` and the built-in :exc:`TypeError`.
54
55   Since :meth:`Message.add_payload` is deprecated, this exception is rarely raised
56   in practice.  However the exception may also be raised if the :meth:`attach`
57   method is called on an instance of a class derived from
58   :class:`~email.mime.nonmultipart.MIMENonMultipart` (e.g.
59   :class:`~email.mime.image.MIMEImage`).
60
61Here's the list of the defects that the :class:`~email.mime.parser.FeedParser`
62can find while parsing messages.  Note that the defects are added to the message
63where the problem was found, so for example, if a message nested inside a
64:mimetype:`multipart/alternative` had a malformed header, that nested message
65object would have a defect, but the containing messages would not.
66
67All defect classes are subclassed from :class:`email.errors.MessageDefect`, but
68this class is *not* an exception!
69
70.. versionadded:: 2.4
71   All the defect classes were added.
72
73* :class:`NoBoundaryInMultipartDefect` -- A message claimed to be a multipart,
74  but had no :mimetype:`boundary` parameter.
75
76* :class:`StartBoundaryNotFoundDefect` -- The start boundary claimed in the
77  :mailheader:`Content-Type` header was never found.
78
79* :class:`FirstHeaderLineIsContinuationDefect` -- The message had a continuation
80  line as its first header line.
81
82* :class:`MisplacedEnvelopeHeaderDefect` - A "Unix From" header was found in the
83  middle of a header block.
84
85* :class:`MalformedHeaderDefect` -- A header was found that was missing a colon,
86  or was otherwise malformed.
87
88* :class:`MultipartInvariantViolationDefect` -- A message claimed to be a
89  :mimetype:`multipart`, but no subparts were found.  Note that when a message has
90  this defect, its :meth:`is_multipart` method may return false even though its
91  content type claims to be :mimetype:`multipart`.
92