Package email :: Module charset :: Class Charset
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_ClassType Charset

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.

Instance Methods [hide private]
 
__init__(self, input_charset='us-ascii')
 
__str__(self)
 
__repr__(self)
 
__eq__(self, other)
 
__ne__(self, other)
 
get_body_encoding(self)
Return the content-transfer-encoding used for body encoding.
 
convert(self, s)
Convert a string from the input_codec to the output_codec.
 
to_splittable(self, s)
Convert a possibly multibyte string to a safely splittable format.
 
from_splittable(self, ustr, to_output=True)
Convert a splittable string back into an encoded string.
 
get_output_charset(self)
Return the output character set.
 
encoded_header_len(self, s)
Return the length of the encoded header string.
 
header_encode(self, s, convert=False)
Header-encode a string, optionally converting it to output_charset.
 
body_encode(self, s, convert=True)
Body-encode a string and convert it to output_charset.
Method Details [hide private]

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.

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.

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_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.

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.