Properly-working DEFLATE compression is elusive in Python. Thanks to wtolson, I’ve found such a solution.

This is an example framework for establishing the compression and decompression objects:

def activate_zlib():
    import zlib

    wbits = -zlib.MAX_WBITS

    compress = zlib.compressobj(level, zlib.DEFLATED, wbits)

    compressor = lambda x: compress.compress(x) + \
                            compress.flush(zlib.Z_SYNC_FLUSH)

    decompress = zlib.decompressobj(wbits)
    
    decompressor = lambda x: decompress.decompress(x) + \
                                decompress.flush()
    
    return (compressor, decompressor)

With this example, you’ll pass all of your outgoing data through the compressor, and all of your incoming data to the decompressor. As always, you’ll do a read-loop until you’ve decompressed the expected number of bytes.