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/Doc/library/email.util.rst

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  1:mod:`email`: Miscellaneous utilities
  2-------------------------------------
  3
  4.. module:: email.utils
  5   :synopsis: Miscellaneous email package utilities.
  6
  7
  8There are several useful utilities provided in the :mod:`email.utils` module:
  9
 10
 11.. function:: quote(str)
 12
 13   Return a new string with backslashes in *str* replaced by two backslashes, and
 14   double quotes replaced by backslash-double quote.
 15
 16
 17.. function:: unquote(str)
 18
 19   Return a new string which is an *unquoted* version of *str*. If *str* ends and
 20   begins with double quotes, they are stripped off.  Likewise if *str* ends and
 21   begins with angle brackets, they are stripped off.
 22
 23
 24.. function:: parseaddr(address)
 25
 26   Parse address -- which should be the value of some address-containing field such
 27   as :mailheader:`To` or :mailheader:`Cc` -- into its constituent *realname* and
 28   *email address* parts.  Returns a tuple of that information, unless the parse
 29   fails, in which case a 2-tuple of ``('', '')`` is returned.
 30
 31
 32.. function:: formataddr(pair)
 33
 34   The inverse of :meth:`parseaddr`, this takes a 2-tuple of the form ``(realname,
 35   email_address)`` and returns the string value suitable for a :mailheader:`To` or
 36   :mailheader:`Cc` header.  If the first element of *pair* is false, then the
 37   second element is returned unmodified.
 38
 39
 40.. function:: getaddresses(fieldvalues)
 41
 42   This method returns a list of 2-tuples of the form returned by ``parseaddr()``.
 43   *fieldvalues* is a sequence of header field values as might be returned by
 44   :meth:`Message.get_all`.  Here's a simple example that gets all the recipients
 45   of a message::
 46
 47      from email.utils import getaddresses
 48
 49      tos = msg.get_all('to', [])
 50      ccs = msg.get_all('cc', [])
 51      resent_tos = msg.get_all('resent-to', [])
 52      resent_ccs = msg.get_all('resent-cc', [])
 53      all_recipients = getaddresses(tos + ccs + resent_tos + resent_ccs)
 54
 55
 56.. function:: parsedate(date)
 57
 58   Attempts to parse a date according to the rules in :rfc:`2822`. however, some
 59   mailers don't follow that format as specified, so :func:`parsedate` tries to
 60   guess correctly in such cases.  *date* is a string containing an :rfc:`2822`
 61   date, such as  ``"Mon, 20 Nov 1995 19:12:08 -0500"``.  If it succeeds in parsing
 62   the date, :func:`parsedate` returns a 9-tuple that can be passed directly to
 63   :func:`time.mktime`; otherwise ``None`` will be returned.  Note that indexes 6,
 64   7, and 8 of the result tuple are not usable.
 65
 66
 67.. function:: parsedate_tz(date)
 68
 69   Performs the same function as :func:`parsedate`, but returns either ``None`` or
 70   a 10-tuple; the first 9 elements make up a tuple that can be passed directly to
 71   :func:`time.mktime`, and the tenth is the offset of the date's timezone from UTC
 72   (which is the official term for Greenwich Mean Time) [#]_.  If the input string
 73   has no timezone, the last element of the tuple returned is ``None``.  Note that
 74   indexes 6, 7, and 8 of the result tuple are not usable.
 75
 76
 77.. function:: mktime_tz(tuple)
 78
 79   Turn a 10-tuple as returned by :func:`parsedate_tz` into a UTC timestamp.  It
 80   the timezone item in the tuple is ``None``, assume local time.  Minor
 81   deficiency: :func:`mktime_tz` interprets the first 8 elements of *tuple* as a
 82   local time and then compensates for the timezone difference.  This may yield a
 83   slight error around changes in daylight savings time, though not worth worrying
 84   about for common use.
 85
 86
 87.. function:: formatdate([timeval[, localtime][, usegmt]])
 88
 89   Returns a date string as per :rfc:`2822`, e.g.::
 90
 91      Fri, 09 Nov 2001 01:08:47 -0000
 92
 93   Optional *timeval* if given is a floating point time value as accepted by
 94   :func:`time.gmtime` and :func:`time.localtime`, otherwise the current time is
 95   used.
 96
 97   Optional *localtime* is a flag that when ``True``, interprets *timeval*, and
 98   returns a date relative to the local timezone instead of UTC, properly taking
 99   daylight savings time into account. The default is ``False`` meaning UTC is
100   used.
101
102   Optional *usegmt* is a flag that when ``True``, outputs a  date string with the
103   timezone as an ascii string ``GMT``, rather than a numeric ``-0000``. This is
104   needed for some protocols (such as HTTP). This only applies when *localtime* is
105   ``False``.
106
107   .. versionadded:: 2.4
108
109
110.. function:: make_msgid([idstring])
111
112   Returns a string suitable for an :rfc:`2822`\ -compliant
113   :mailheader:`Message-ID` header.  Optional *idstring* if given, is a string used
114   to strengthen the uniqueness of the message id.
115
116
117.. function:: decode_rfc2231(s)
118
119   Decode the string *s* according to :rfc:`2231`.
120
121
122.. function:: encode_rfc2231(s[, charset[, language]])
123
124   Encode the string *s* according to :rfc:`2231`.  Optional *charset* and
125   *language*, if given is the character set name and language name to use.  If
126   neither is given, *s* is returned as-is.  If *charset* is given but *language*
127   is not, the string is encoded using the empty string for *language*.
128
129
130.. function:: collapse_rfc2231_value(value[, errors[, fallback_charset]])
131
132   When a header parameter is encoded in :rfc:`2231` format,
133   :meth:`Message.get_param` may return a 3-tuple containing the character set,
134   language, and value.  :func:`collapse_rfc2231_value` turns this into a unicode
135   string.  Optional *errors* is passed to the *errors* argument of the built-in
136   :func:`unicode` function; it defaults to ``replace``.  Optional
137   *fallback_charset* specifies the character set to use if the one in the
138   :rfc:`2231` header is not known by Python; it defaults to ``us-ascii``.
139
140   For convenience, if the *value* passed to :func:`collapse_rfc2231_value` is not
141   a tuple, it should be a string and it is returned unquoted.
142
143
144.. function:: decode_params(params)
145
146   Decode parameters list according to :rfc:`2231`.  *params* is a sequence of
147   2-tuples containing elements of the form ``(content-type, string-value)``.
148
149.. versionchanged:: 2.4
150   The :func:`dump_address_pair` function has been removed; use :func:`formataddr`
151   instead.
152
153.. versionchanged:: 2.4
154   The :func:`decode` function has been removed; use the
155   :meth:`Header.decode_header` method instead.
156
157.. versionchanged:: 2.4
158   The :func:`encode` function has been removed; use the :meth:`Header.encode`
159   method instead.
160
161.. rubric:: Footnotes
162
163.. [#] Note that the sign of the timezone offset is the opposite of the sign of the
164   ``time.timezone`` variable for the same timezone; the latter variable follows
165   the POSIX standard while this module follows :rfc:`2822`.
166