def _formatparam(param, value=None, quote=True): """Convenience function to format and return a key=value pair. This will quote the value if needed or if quote is true. If value is a three tuple (charset, language, value), it will be encoded according to RFC2231 rules. If it contains non-ascii characters it will likewise be encoded according to RFC2231 rules, using the utf-8 charset and a null language. """ if value is not None and len(value) > 0: # A tuple is used for RFC 2231 encoded parameter values where items # are (charset, language, value). charset is a string, not a Charset # instance. RFC 2231 encoded values are never quoted, per RFC. if isinstance(value, tuple): # Encode as per RFC 2231 param += '*' value = utils.encode_rfc2231(value[2], value[0], value[1]) return '%s=%s' % (param, value) else: try: value.encode('ascii') except UnicodeEncodeError: param += '*' value = utils.encode_rfc2231(value, 'utf-8', '') return '%s=%s' % (param, value) # BAW: Please check this. I think that if quote is set it should # force quoting even if not necessary. if quote or tspecials.search(value): return '%s="%s"' % (param, utils.quote(value)) else: return '%s=%s' % (param, value) else: return param