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- Charset
class Charset |
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Map character sets to their email properties.
This class provides information about the requirements imposed on email
for a specific character set. It also provides convenience routines for
converting between character sets, given the availability of the
applicable codecs. Given a character set, it will do its best to provide
information on how to use that character set in an email in an
RFC-compliant way.
Certain character sets must be encoded with quoted-printable or base64
when used in email headers or bodies. Certain character sets must be
converted outright, and are not allowed in email. Instances of this
module expose the following information about a character set:
input_charset: The initial character set specified. Common aliases
are converted to their `official' email names (e.g. latin_1
is converted to iso-8859-1). Defaults to 7-bit us-ascii.
header_encoding: If the character set must be encoded before it can be
used in an email header, this attribute will be set to
Charset.QP (for quoted-printable), Charset.BASE64 (for
base64 encoding), or Charset.SHORTEST for the shortest of
QP or BASE64 encoding. Otherwise, it will be None.
body_encoding: Same as header_encoding, but describes the encoding for the
mail message's body, which indeed may be different than the
header encoding. Charset.SHORTEST is not allowed for
body_encoding.
output_charset: Some character sets must be converted before the can be
used in email headers or bodies. If the input_charset is
one of them, this attribute will contain the name of the
charset output will be converted to. Otherwise, it will
be None.
input_codec: The name of the Python codec used to convert the
input_charset to Unicode. If no conversion codec is
necessary, this attribute will be None.
output_codec: The name of the Python codec used to convert Unicode
to the output_charset. If no conversion codec is necessary,
this attribute will have the same value as the input_codec.
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Methods defined here:
- __eq__(self, other)
- __init__(self, input_charset='us-ascii')
- __ne__(self, other)
- __repr__ = __str__(self)
- __str__(self)
- body_encode(self, s, convert=True)
- Body-encode a string and convert it to output_charset.
If convert is True (the default), the string will be converted from
the input charset to output charset automatically. Unlike
header_encode(), there are no issues with byte boundaries and
multibyte charsets in email bodies, so this is usually pretty safe.
The type of encoding (base64 or quoted-printable) will be based on
self.body_encoding.
- convert(self, s)
- Convert a string from the input_codec to the output_codec.
- encoded_header_len(self, s)
- Return the length of the encoded header string.
- from_splittable(self, ustr, to_output=True)
- Convert a splittable string back into an encoded string.
Uses the proper codec to try and convert the string from Unicode back
into an encoded format. Return the string as-is if it is not Unicode,
or if it could not be converted from Unicode.
Characters that could not be converted from Unicode will be replaced
with an appropriate character (usually '?').
If to_output is True (the default), uses output_codec to convert to an
encoded format. If to_output is False, uses input_codec.
- get_body_encoding(self)
- Return the content-transfer-encoding used for body encoding.
This is either the string `quoted-printable' or `base64' depending on
the encoding used, or it is a function in which case you should call
the function with a single argument, the Message object being
encoded. The function should then set the Content-Transfer-Encoding
header itself to whatever is appropriate.
Returns "quoted-printable" if self.body_encoding is QP.
Returns "base64" if self.body_encoding is BASE64.
Returns "7bit" otherwise.
- get_output_charset(self)
- Return the output character set.
This is self.output_charset if that is not None, otherwise it is
self.input_charset.
- header_encode(self, s, convert=False)
- Header-encode a string, optionally converting it to output_charset.
If convert is True, the string will be converted from the input
charset to the output charset automatically. This is not useful for
multibyte character sets, which have line length issues (multibyte
characters must be split on a character, not a byte boundary); use the
high-level Header class to deal with these issues. convert defaults
to False.
The type of encoding (base64 or quoted-printable) will be based on
self.header_encoding.
- to_splittable(self, s)
- Convert a possibly multibyte string to a safely splittable format.
Uses the input_codec to try and convert the string to Unicode, so it
can be safely split on character boundaries (even for multibyte
characters).
Returns the string as-is if it isn't known how to convert it to
Unicode with the input_charset.
Characters that could not be converted to Unicode will be replaced
with the Unicode replacement character U+FFFD.
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