问题出在你的dec2hex代码中：

The problem is in your dec2hex code:

def dec2hex(d):
    """return a two character hexadecimal string representation of integer d"""
    r = "%X" % d
    return r if len(r) > 1 else r+r

当值小于16时，你想要这样：

When your value is less than 16, you're duplicating it to get the value, in other words, multiplying it by 17. You want this:

def dec2hex(d):
    """return a two character hexadecimal string representation of integer d"""
    return "%02X" % d