c-types Structure and equality with bytes/bytearray

[Michael Hull]

Hello everyone,

I've been working with ctypes recently, and I've come across what seems to
be some slightly confusing behaviour, when comparing ctype's Structure
against `bytes` and `bytearray` objects


import ctypes



class Int(ctypes.Structure):

    _fields_ = [("first_16",  ctypes.c_int8),

                ("second_16", ctypes.c_int8)]



    def serialise(self):

        return ctypes.string_at(ctypes.addressof(self),

                                ctypes.sizeof(self))



i_obj= Int(first_16= 65, second_16=66)

print(i_obj.first_16, i_obj.second_16)



i_bytes = i_obj.serialise()

print(list(i_bytes))

assert type(i_bytes) == bytes



i_bytearray = bytearray(i_bytes)





print("obj == bytes     =>", i_obj==i_bytes)

print("bytes == obj     =>", i_bytes==i_obj)

print("obj == bytearray =>", i_obj==i_bytearray)

print("bytearray == obj =>", i_bytearray==i_obj)




When I run this (Python 3.6, and Python2.7) , the final 4 print statements
give the following:

"""

obj == bytes     => False

bytes == obj     => False

obj == bytearray => True

bytearray == obj => True

"""

Is this a bit strange -- my understanding was that `bytes` and `bytearray`
would normally be expected to work quite interchangeably with each other?


It also means that:

bytearray == obj   => True

bytes == bytearray => True

bytes == obj       => False


If anyone has any experience in this area, and can let me know if I'm
overlooking something silly, and guidance would be gratefully appreciated.
Alternatively, I am happy to open up a bug-report if this looks like
unexpected behaviour?


Best wishes,



Mike