def get_centigrade():
    """ Blocking prompt for setting C/F preference. """
    from x84.bbs import getterminal, getsession, echo
    term = getterminal()
    session = getsession()
    if bool(session.user.handle == 'anonymous'):
        return
    echo(u''.join((u'\r\n\r\n', term.yellow(u'Celcius'), term.bold_yellow(
        u'('), term.bold_yellow_reverse(u'C'), term.bold_yellow(u')'),
        u' or ', term.yellow(u'Fahrenheit'), term.bold_yellow(u'('), term.
        bold_yellow_reverse(u'F'), term.bold_yellow(u')'), u'? ')))
    while True:
        inp = term.inkey()
        if inp in (u'c', u'C'):
            session.user['centigrade'] = True
            session.user.save()
            break
        elif inp in (u'f', u'F'):
            session.user['centigrade'] = False
            session.user.save()
            break
        elif inp in (u'q', u'Q', term.KEY_EXIT):
            break
