bpo-35035: Rename email.utils documentation to email.utils.rst (GH-10023)

I'll watch for 404 on the old URL and will setup an HTTP redirection if needed.
(cherry picked from commit 361e8683e7340c600b22f4a514b81448ccec66dc)

Co-authored-by: Zhiming Wang <github@zmwang.pw>

1 files changed, 218 insertions, 0 deletions

diff --git a/Doc/library/email.utils.rst b/Doc/library/email.utils.rst
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+:mod:`email.utils`: Miscellaneous utilities
+-------------------------------------------
+
+.. module:: email.utils
+   :synopsis: Miscellaneous email package utilities.
+
+**Source code:** :source:`Lib/email/utils.py`
+
+--------------
+
+There are a couple of useful utilities provided in the :mod:`email.utils`
+module:
+
+.. function:: localtime(dt=None)
+
+    Return local time as an aware datetime object.  If called without
+    arguments, return current time.  Otherwise *dt* argument should be a
+    :class:`~datetime.datetime` instance, and it is converted to the local time
+    zone according to the system time zone database.  If *dt* is naive (that
+    is, ``dt.tzinfo`` is ``None``), it is assumed to be in local time.  In this
+    case, a positive or zero value for *isdst* causes ``localtime`` to presume
+    initially that summer time (for example, Daylight Saving Time) is or is not
+    (respectively) in effect for the specified time.  A negative value for
+    *isdst* causes the ``localtime`` to attempt to divine whether summer time
+    is in effect for the specified time.
+
+    .. versionadded:: 3.3
+
+
+.. function:: make_msgid(idstring=None, domain=None)
+
+   Returns a string suitable for an :rfc:`2822`\ -compliant
+   :mailheader:`Message-ID` header.  Optional *idstring* if given, is a string
+   used to strengthen the uniqueness of the message id.  Optional *domain* if
+   given provides the portion of the msgid after the '@'.  The default is the
+   local hostname.  It is not normally necessary to override this default, but
+   may be useful certain cases, such as a constructing distributed system that
+   uses a consistent domain name across multiple hosts.
+
+   .. versionchanged:: 3.2
+      Added the *domain* keyword.
+
+
+The remaining functions are part of the legacy (``Compat32``) email API.  There
+is no need to directly use these with the new API, since the parsing and
+formatting they provide is done automatically by the header parsing machinery
+of the new API.
+
+
+.. function:: quote(str)
+
+   Return a new string with backslashes in *str* replaced by two backslashes, and
+   double quotes replaced by backslash-double quote.
+
+
+.. function:: unquote(str)
+
+   Return a new string which is an *unquoted* version of *str*. If *str* ends and
+   begins with double quotes, they are stripped off.  Likewise if *str* ends and
+   begins with angle brackets, they are stripped off.
+
+
+.. function:: parseaddr(address)
+
+   Parse address -- which should be the value of some address-containing field such
+   as :mailheader:`To` or :mailheader:`Cc` -- into its constituent *realname* and
+   *email address* parts.  Returns a tuple of that information, unless the parse
+   fails, in which case a 2-tuple of ``('', '')`` is returned.
+
+
+.. function:: formataddr(pair, charset='utf-8')
+
+   The inverse of :meth:`parseaddr`, this takes a 2-tuple of the form ``(realname,
+   email_address)`` and returns the string value suitable for a :mailheader:`To` or
+   :mailheader:`Cc` header.  If the first element of *pair* is false, then the
+   second element is returned unmodified.
+
+   Optional *charset* is the character set that will be used in the :rfc:`2047`
+   encoding of the ``realname`` if the ``realname`` contains non-ASCII
+   characters.  Can be an instance of :class:`str` or a
+   :class:`~email.charset.Charset`.  Defaults to ``utf-8``.
+
+   .. versionchanged:: 3.3
+      Added the *charset* option.
+
+
+.. function:: getaddresses(fieldvalues)
+
+   This method returns a list of 2-tuples of the form returned by ``parseaddr()``.
+   *fieldvalues* is a sequence of header field values as might be returned by
+   :meth:`Message.get_all <email.message.Message.get_all>`.  Here's a simple
+   example that gets all the recipients of a message::
+
+      from email.utils import getaddresses
+
+      tos = msg.get_all('to', [])
+      ccs = msg.get_all('cc', [])
+      resent_tos = msg.get_all('resent-to', [])
+      resent_ccs = msg.get_all('resent-cc', [])
+      all_recipients = getaddresses(tos + ccs + resent_tos + resent_ccs)
+
+
+.. function:: parsedate(date)
+
+   Attempts to parse a date according to the rules in :rfc:`2822`. however, some
+   mailers don't follow that format as specified, so :func:`parsedate` tries to
+   guess correctly in such cases.  *date* is a string containing an :rfc:`2822`
+   date, such as  ``"Mon, 20 Nov 1995 19:12:08 -0500"``.  If it succeeds in parsing
+   the date, :func:`parsedate` returns a 9-tuple that can be passed directly to
+   :func:`time.mktime`; otherwise ``None`` will be returned.  Note that indexes 6,
+   7, and 8 of the result tuple are not usable.
+
+
+.. function:: parsedate_tz(date)
+
+   Performs the same function as :func:`parsedate`, but returns either ``None`` or
+   a 10-tuple; the first 9 elements make up a tuple that can be passed directly to
+   :func:`time.mktime`, and the tenth is the offset of the date's timezone from UTC
+   (which is the official term for Greenwich Mean Time) [#]_.  If the input string
+   has no timezone, the last element of the tuple returned is ``None``.  Note that
+   indexes 6, 7, and 8 of the result tuple are not usable.
+
+
+.. function:: parsedate_to_datetime(date)
+
+   The inverse of :func:`format_datetime`.  Performs the same function as
+   :func:`parsedate`, but on success returns a :mod:`~datetime.datetime`.  If
+   the input date has a timezone of ``-0000``, the ``datetime`` will be a naive
+   ``datetime``, and if the date is conforming to the RFCs it will represent a
+   time in UTC but with no indication of the actual source timezone of the
+   message the date comes from.  If the input date has any other valid timezone
+   offset, the ``datetime`` will be an aware ``datetime`` with the
+   corresponding a :class:`~datetime.timezone` :class:`~datetime.tzinfo`.
+
+   .. versionadded:: 3.3
+
+
+.. function:: mktime_tz(tuple)
+
+   Turn a 10-tuple as returned by :func:`parsedate_tz` into a UTC
+   timestamp (seconds since the Epoch).  If the timezone item in the
+   tuple is ``None``, assume local time.
+
+
+.. function:: formatdate(timeval=None, localtime=False, usegmt=False)
+
+   Returns a date string as per :rfc:`2822`, e.g.::
+
+      Fri, 09 Nov 2001 01:08:47 -0000
+
+   Optional *timeval* if given is a floating point time value as accepted by
+   :func:`time.gmtime` and :func:`time.localtime`, otherwise the current time is
+   used.
+
+   Optional *localtime* is a flag that when ``True``, interprets *timeval*, and
+   returns a date relative to the local timezone instead of UTC, properly taking
+   daylight savings time into account. The default is ``False`` meaning UTC is
+   used.
+
+   Optional *usegmt* is a flag that when ``True``, outputs a  date string with the
+   timezone as an ascii string ``GMT``, rather than a numeric ``-0000``. This is
+   needed for some protocols (such as HTTP). This only applies when *localtime* is
+   ``False``.  The default is ``False``.
+
+
+.. function:: format_datetime(dt, usegmt=False)
+
+   Like ``formatdate``, but the input is a :mod:`datetime` instance.  If it is
+   a naive datetime, it is assumed to be "UTC with no information about the
+   source timezone", and the conventional ``-0000`` is used for the timezone.
+   If it is an aware ``datetime``, then the numeric timezone offset is used.
+   If it is an aware timezone with offset zero, then *usegmt* may be set to
+   ``True``, in which case the string ``GMT`` is used instead of the numeric
+   timezone offset.  This provides a way to generate standards conformant HTTP
+   date headers.
+
+   .. versionadded:: 3.3
+
+
+.. function:: decode_rfc2231(s)
+
+   Decode the string *s* according to :rfc:`2231`.
+
+
+.. function:: encode_rfc2231(s, charset=None, language=None)
+
+   Encode the string *s* according to :rfc:`2231`.  Optional *charset* and
+   *language*, if given is the character set name and language name to use.  If
+   neither is given, *s* is returned as-is.  If *charset* is given but *language*
+   is not, the string is encoded using the empty string for *language*.
+
+
+.. function:: collapse_rfc2231_value(value, errors='replace', fallback_charset='us-ascii')
+
+   When a header parameter is encoded in :rfc:`2231` format,
+   :meth:`Message.get_param <email.message.Message.get_param>` may return a
+   3-tuple containing the character set,
+   language, and value.  :func:`collapse_rfc2231_value` turns this into a unicode
+   string.  Optional *errors* is passed to the *errors* argument of :class:`str`'s
+   :func:`~str.encode` method; it defaults to ``'replace'``.  Optional
+   *fallback_charset* specifies the character set to use if the one in the
+   :rfc:`2231` header is not known by Python; it defaults to ``'us-ascii'``.
+
+   For convenience, if the *value* passed to :func:`collapse_rfc2231_value` is not
+   a tuple, it should be a string and it is returned unquoted.
+
+
+.. function:: decode_params(params)
+
+   Decode parameters list according to :rfc:`2231`.  *params* is a sequence of
+   2-tuples containing elements of the form ``(content-type, string-value)``.
+
+
+.. rubric:: Footnotes
+
+.. [#] Note that the sign of the timezone offset is the opposite of the sign of the
+   ``time.timezone`` variable for the same timezone; the latter variable follows
+   the POSIX standard while this module follows :rfc:`2822`.