mygzip.py

import struct, time, zlib

def generate_gzip():
    # Migration Python2 to 3 https://stackoverflow.com/a/44387566/2137364
    # Yield a gzip file header first.
    yield (
        b'\037\213\010\000' + # Gzip file, deflate, no filename
        struct.pack('<L', int(time.time())) +  # compression start time
        b'\002\377'  # maximum compression, no OS specified
    )

    # bookkeeping: the compression state, running CRC and total length
    compressor = zlib.compressobj(
        9, zlib.DEFLATED, -zlib.MAX_WBITS, zlib.DEF_MEM_LEVEL, 0)
    crc = zlib.crc32(b'')
    length = 0

    for x in range(10000):
        data = "this is my line: {}\n".format(x).encode()
        chunk = compressor.compress(data)
        if chunk:
            yield chunk
        crc = zlib.crc32(data, crc) & 0xffffffff
        length += len(data)

    # Finishing off, send remainder of the compressed data, and CRC and length
    yield compressor.flush()
    yield struct.pack("<2L", crc, length & 0xffffffff)
    
    
with open('out.gz', 'wb') as f:
    for data in generate_gzip():
        f.write( data )