def parse_encoding(fp):
    """Deduce the encoding of a source file from magic comment.

    It does this in the same way as the `Python interpreter`__

    .. __: https://docs.python.org/3.4/reference/lexical_analysis.html#encoding-declarations

    The ``fp`` argument should be a seekable file object.

    (From Jeff Dairiki)
    """
    pos = fp.tell()
    fp.seek(0)
    try:
        line1 = fp.readline()
        has_bom = line1.startswith(codecs.BOM_UTF8)
        if has_bom:
            line1 = line1[len(codecs.BOM_UTF8):]

        m = PYTHON_MAGIC_COMMENT_re.match(line1)
        if not m:
            try:
                import parser
                parser.suite(line1.decode('latin-1'))
            except (__HOLE__, SyntaxError, UnicodeEncodeError):
                # Either it's a real syntax error, in which case the source is
                # not valid python source, or line2 is a continuation of line1,
                # in which case we don't want to scan line2 for a magic
                # comment.
                pass
            else:
                line2 = fp.readline()
                m = PYTHON_MAGIC_COMMENT_re.match(line2)

        if has_bom:
            if m:
                magic_comment_encoding = m.group(1).decode('latin-1')
                if magic_comment_encoding != 'utf-8':
                    raise SyntaxError(
                        'encoding problem: {0} with BOM'.format(
                            magic_comment_encoding))
            return 'utf-8'
        elif m:
            return m.group(1).decode('latin-1')
        else:
            return None
    finally:
        fp.seek(pos)
dataset/ETHPy150Open python-babel/babel/babel/util.py/parse_encoding