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Version 1 of the email package was bundled with Python releases up
to Python 2.2.1. Version 2 was developed for the Python 2.3 release, and backported to Python
2.2.2. It was also available as a separate distutils based package. email
version 2 is almost entirely backward compatible with version 1, with the following
differences:
- The email.Header and email.Charset
modules have been added.
- The pickle format for Message instances has changed. Since this
was never (and still isn't) formally defined, this isn't considered a backward
incompatibility. However if your application pickles and unpickles Message
instances, be aware that in email version 2, Message
instances now have private variables _charset and _default_type.
- Several methods in the Message class have been deprecated, or
their signatures changed. Also, many new methods have been added. See the documentation
for the Message class for details. The changes should be completely
backward compatible.
- The object structure has changed in the face of message/rfc822
content types. In email version 1, such a type would be
represented by a scalar payload, i.e. the container message's is_multipart()
returned false, get_payload() was not a list object, but a single Message instance.
This structure was inconsistent with the rest of the package, so the object
representation for message/rfc822 content types was changed.
In email version 2, the container does return True
from is_multipart(), and get_payload()
returns a list containing a single Message item.
Note that this is one place that backward compatibility could not be completely
maintained. However, if you're already testing the return type of get_payload(),
you should be fine. You just need to make sure your code doesn't do a set_payload()
with a Message instance on a container with a content type of message/rfc822.
- The Parser constructor's strict argument was added,
and its parse() and parsestr() methods
grew a headersonly argument. The strict flag was also added to
functions email.message_from_file() and email.message_from_string().
- Generator.__call__() is deprecated; use Generator.flatten()
instead. The Generator class has also grown the clone()
method.
- The DecodedGenerator class in the email.Generator
module was added.
- The intermediate base classes MIMENonMultipart and MIMEMultipart have been added, and interposed in the class hierarchy
for most of the other MIME-related derived classes.
- The _encoder argument to the MIMEText constructor has
been deprecated. Encoding now happens implicitly based on the _charset
argument.
- The following functions in the email.Utils module have been
deprecated: dump_address_pairs(), decode(),
and encode(). The following functions have been added to the
module: make_msgid(), decode_rfc2231(),
encode_rfc2231(), and decode_params().
- The non-public function email.Iterators._structure() was
added.
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