safeeval.py 文件源码

def test_expr(expr, allowed_codes):
    """test_expr(expr, allowed_codes) -> codeobj

    Test that the expression contains only the listed opcodes.
    If the expression is valid and contains only allowed codes,
    return the compiled code object. Otherwise raise a ValueError
    """
    import dis
    allowed_codes = [dis.opmap[c] for c in allowed_codes]
    try:
        c = compile(expr, "", "eval")
    except SyntaxError:
        raise ValueError("%s is not a valid expression" % expr)
    codes = _get_opcodes(c)
    for code in codes:
        if code not in allowed_codes:
            raise ValueError("opcode %s not allowed" % dis.opname[code])
    return c