signing.py

def canonical_jsonify(json_node):
    # Escape character | quote | backslash | high surrogate not followed by low, or low surrogate not following
    # a high surrogate
    replace_regex = r'[\u0000-\u001F]|\"|\\|[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?:[^\uD800-\uDBFF]|^)[\uDC00-\uDFFF]'
    to_slash_escape = {
        '\b': '\\b',
        '\t': '\\t',
        '\n': '\\n',
        '\f': '\\f',
        '\r': '\\r',
        '\"': '\\\"',
        '\\': '\\\\',
    }

    def escape_match(match):
        character = match.group()
        # Use slash escape if possible, otherwise use unicode escape
        if character in to_slash_escape:
            return to_slash_escape[character]
        else:
            return '\\u{0:04X}'.format(ord(character))

    def do_encode(json_node, depth):
        if depth > 100:
            raise ValueError('Max depth exceeded. Structure is probably recursive.')
        if json_node is None:
            return 'null'
        elif isinstance(json_node, bool):
            return 'true' if json_node else 'false'
        elif isinstance(json_node, int):
            return str(json_node)
        elif isinstance(json_node, float):
            exponent = int(math.log10(abs(json_node)))
            mantissa = json_node / (10 ** exponent)
            return '{}E{}'.format(mantissa, exponent)
        elif isinstance(json_node, str):
            return '"{}"'.format(re.sub(replace_regex, escape_match, json_node))
        elif isinstance(json_node, dict):
            sorted_kv_pairs = sorted(json_node.items(), key=lambda pair: pair[0])
            node_contents = ','.join([
                ':'.join([do_encode(x, depth + 1) for x in [k, v]])
                for k, v in sorted_kv_pairs
            ])
            return '{{{}}}'.format(node_contents)
        elif isinstance(json_node, list):
            node_contents = ','.join([do_encode(x, depth + 1) for x in json_node])
            return '[{}]'.format(node_contents)
        else:
            raise ValueError('Unknown type: '.format(type(json_node)))

    return do_encode(json_node, 0)