How to do a safe binary comparison in Python?

I have the following piece of code that is throwing a warning:

UnicodeWarning: Unicode equal comparison failed to convert both arguments to Unicode - interpreting them as being unequal

try:
    f = open_old(filename, "rb")
    aBuf = f.read(4)
    f.close()
except:
    aBuf=b''
if aBuf[:3] == b'\xEF\xBB\xBF':
    print("...")

What is the proper way of reading 3 bytes from the file and checking their values.

I am looking for a solution that would开发者_如何转开发 work properly in Python 2.6 and newwer (including 3.x).

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The solution is to convert the string to bytes after you read it: aBuf = bytes(f.read(4)).