Controls for how messages are interpreted and formatted.
Most of the classes and many of the methods in the email package accept
Policy objects as parameters. A Policy object contains a set of values and
functions that control how input is interpreted and how output is rendered.
For example, the parameter 'raise_on_defect' controls whether or not an RFC
violation results in an error being raised or not, while 'max_line_length'
controls the maximum length of output lines when a Message is serialized.
Any valid attribute may be overridden when a Policy is created by passing
it as a keyword argument to the constructor. Policy objects are immutable,
but a new Policy object can be created with only certain values changed by
calling the Policy instance with keyword arguments. Policy objects can
also be added, producing a new Policy object in which the non-default
attributes set in the right hand operand overwrite those specified in the
left operand.
Settable attributes:
raise_on_defect -- If true, then defects should be raised as errors.
Default: False.
linesep -- string containing the value to use as separation
between output lines. Default '\n'.
cte_type -- Type of allowed content transfer encodings
7bit -- ASCII only
8bit -- Content-Transfer-Encoding: 8bit is allowed
Default: 8bit. Also controls the disposition of
(RFC invalid) binary data in headers; see the
documentation of the binary_fold method.
max_line_length -- maximum length of lines, excluding 'linesep',
during serialization. None or 0 means no line
wrapping is done. Default is 78.
mangle_from_ -- a flag that, when True escapes From_ lines in the
body of the message by putting a '>' in front of
them. This is used when the message is being
serialized by a generator. Default: False.
message_factory -- the class to use to create new message objects.
If the value is None, the default is Message.
verify_generated_headers
-- if true, the generator verifies that each header
they are properly folded, so that a parser won't
treat it as multiple headers, start-of-body, or
part of another header.
This is a check against custom Header & fold()
implementations.
PROVISIONAL
The API extensions enabled by this policy are currently provisional.
Refer to the documentation for details.
This policy adds new header parsing and folding algorithms. Instead of
simple strings, headers are custom objects with custom attributes
depending on the type of the field. The folding algorithm fully
implements RFCs 2047 and 5322.
In addition to the settable attributes listed above that apply to
all Policies, this policy adds the following additional attributes:
utf8 -- if False (the default) message headers will be
serialized as ASCII, using encoded words to encode
any non-ASCII characters in the source strings. If
True, the message headers will be serialized using
utf8 and will not contain encoded words (see RFC
6532 for more on this serialization format).
refold_source -- if the value for a header in the Message object
came from the parsing of some source, this attribute
indicates whether or not a generator should refold
that value when transforming the message back into
stream form. The possible values are:
none -- all source values use original folding
long -- source values that have any line that is
longer than max_line_length will be
refolded
all -- all values are refolded.
The default is 'long'.
header_factory -- a callable that takes two arguments, 'name' and
'value', where 'name' is a header field name and
'value' is an unfolded header field value, and
returns a string-like object that represents that
header. A default header_factory is provided that
understands some of the RFC5322 header field types.
(Currently address fields and date fields have
special treatment, while all other fields are
treated as unstructured. This list will be
completed before the extension is marked stable.)
content_manager -- an object with at least two methods: get_content
and set_content. When the get_content or
set_content method of a Message object is called,
it calls the corresponding method of this object,
passing it the message object as its first argument,
and any arguments or keywords that were passed to
it as additional arguments. The default
content_manager is
:data:`~email.contentmanager.raw_data_manager`.