Python IMAP: =?utf-8?Q? in subject string

In MIME terminology, those encoded chunks are called encoded-words. You can decode them like this:

import email.Header
text, encoding = email.Header.decode_header('=?utf-8?Q?Subject?=')[0]

Check out the docs for email.Header for more details.

This is a MIME encoded-word. You can parse it with email.header:

import email.header

def decode_mime_words(s):
    return u''.join(
        word.decode(encoding or 'utf8') if isinstance(word, bytes) else word
        for word, encoding in email.header.decode_header(s))

print(decode_mime_words(u'=?utf-8?Q?Subject=c3=a4?=X=?utf-8?Q?=c3=bc?='))

In Python 3.3+, the parsing classes and functions in email.parser automatically decode "encoded words" in headers if their policy argument is set to policy.default

>>> import email
>>> from email import policy

>>> msg = email.message_from_file(open('message.txt'), policy=policy.default)
>>> msg['from']
'Pepé Le Pew <[email protected]>'

The parsing classes and functions are:

• email.parser.BytesParser
• email.parser.Parser
• email.message_from_bytes
• email.message_from_binary_file
• email.message_from_string
• email.message_from_file

Confusingly, up to at least Python 3.8, the default policy for these parsing functions is not policy.default, but policy.compat32, which does not decode "encoded words".

>>> msg = email.message_from_file(open('message.txt'))
>>> msg['from']
'=?utf-8?q?Pep=C3=A9?= Le Pew <[email protected]>'