This module provides a class Charset for representing character sets and character set conversions in email messages, as well as a character set registry and several convenience methods for manipulating this registry. Instances of Charset are used in several other modules within the email package.
New in version 2.2.2.
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 message 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.
Optional input_charset is as described below; it is always
coerced to lower case. After being alias normalized it is also used
as a lookup into the registry of character sets to find out the header
encoding, body encoding, and output conversion codec to be used for
the character set. For example, if
iso-8859-1, then headers and bodies will
be encoded using quoted-printable and no output conversion codec is
necessary. If input_charset is
euc-jp, then headers will
be encoded with base64, bodies will not be encoded, but output text
will be converted from the
euc-jp character set to the
iso-2022-jp character set.
Charset instances have the following data attributes:
latin_1is converted to
iso-8859-1). Defaults to 7-bit
Charset.BASE64(for base64 encoding), or
Charset.SHORTESTfor the shortest of QP or BASE64 encoding. Otherwise, it will be
Charset.SHORTESTis not allowed for body_encoding.
Charset instances also have the following methods:
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 the string "quoted-printable" if
QP, returns the string
"base64" if body_encoding is
BASE64, and returns the
string "7bit" otherwise.
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 s to Unicode with the input_charset.
Characters that could not be converted to Unicode will be replaced with the Unicode replacement character "U+FFFD".
This method 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, it uses
This is the output_charset attribute if that is not
otherwise it is input_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
higher-level Header class to deal with these issues (see
email.Header). convert defaults to
The type of encoding (base64 or quoted-printable) will be based on the header_encoding attribute.
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
The type of encoding (base64 or quoted-printable) will be based on the body_encoding attribute.
The Charset class also provides a number of methods to support standard operations and built-in functions.
The email.Charset module also provides the following functions for adding new entries to the global character set, alias, and codec registries:
|charset[, header_enc[, body_enc[, output_charset]]])|
charset is the input character set, and must be the canonical name of a character set.
Optional header_enc and body_enc is either
Charset.QP for quoted-printable,
Charset.SHORTEST for the shortest of
quoted-printable or base64 encoding, or
None for no encoding.
SHORTEST is only valid for header_enc. The default is
None for no encoding.
Optional output_charset is the character set that the output should be in. Conversions will proceed from input charset, to Unicode, to the output charset when the method Charset.convert() is called. The default is to output in the same character set as the input.
Both input_charset and output_charset must have Unicode codec entries in the module's character set-to-codec mapping; use add_codec() to add codecs the module does not know about. See the codecs module's documentation for more information.
The global character set registry is kept in the module global
latin-1. canonical is the character set's canonical name, e.g.
The global charset alias registry is kept in the module global
charset is the canonical name of a character set. codecname is the name of a Python codec, as appropriate for the second argument to the unicode() built-in, or to the encode() method of a Unicode string.
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