In example when appending a message with more than one flag in a tuple with imaplib:

print flags
('\\Answered', '\\Seen')

connection.append('INBOX', flags, date, msg)


---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-42-832414ffe4b5> in <module>()
----> 1 connection.append('INBOX', flags, date, msg[1][0][1])

/usr/lib/python2.7/imaplib.py in append(self, mailbox, flags, date_time, message)
    326         if flags:
    327             if (flags[0],flags[-1]) != ('(',')'):
--> 328                 flags = '(%s)' % flags
    329         else:
    330             flags = None

TypeError: not all arguments converted during string formatting


When I have only one flag to append:

print flags
Out[70]: ('\\Answered',)

connection.append('INBOX', flags, date, msg)
Out[74]: ('OK', ['[APPENDUID 1 1012] APPEND completed'])

Any ideas?

Thanks

flags is supposed to be a string. This is not well documented, like much of the module.

Try:
flags = r'(\Answered \Seen)'

Indeed, as with much of the early email related code in the stdlib, the documentation assumes way too much familiarity with the relevant RFC...which is really hard to read.  We should add a few more details to the docs (like FLAGS being a string) even if we don't have the resources to do a full overhaul.

How would this sound as clarification for the flags argument?

*flags* is a space-separated string containing IMAP flags tokens. Must start with ``\``.

Perhaps optionally also provide the list of system flags as given in https://datatracker.ietf.org/doc/html/rfc3501#section-2.3.2