Adding the new opcodes for complex64 means that we have exhausted the 128 byte range of ASCII characters. We need access to the 128-255 range. Thus, we use unicode(opcode).encode('latin-1'), since this code page encoding converts the 128-255 range perfectly. See http://en.wikipedia.org/wiki/ISO/IEC_8859-1 for e.g. and the following

for i in range(255): assert ord(unichr(i).encode('latin-1')) == i

also works.