Python unzipping stream of bytes?

Yes, you can use the zlib module to decompress byte streams:

import zlib

def stream_gzip_decompress(stream):
    dec = zlib.decompressobj(32 + zlib.MAX_WBITS)  # offset 32 to skip the header
    for chunk in stream:
        rv = dec.decompress(chunk)
        if rv:
            yield rv

The offset of 32 signals to the zlib header that the gzip header is expected but skipped.

The S3 key object is an iterator, so you can do:

for data in stream_gzip_decompress(k):
    # do something with the decompressed data

I had to do the same thing and this is how I did it:

import gzip
f = StringIO.StringIO()
k.get_file(f)
f.seek(0) #This is crucial
gzf = gzip.GzipFile(fileobj=f)
file_content = gzf.read()

For Python3x and boto3-

So I used BytesIO to read the compressed file into a buffer object, then I used zipfile to open the decompressed stream as uncompressed data and I was able to get the datum line by line.

import io
import zipfile
import boto3
import sys

s3 = boto3.resource('s3', 'us-east-1')


def stream_zip_file():
    count = 0
    obj = s3.Object(
        bucket_name='MonkeyBusiness',
        key='/Daily/Business/Banana/{current-date}/banana.zip'
    )
    buffer = io.BytesIO(obj.get()["Body"].read())
    print (buffer)
    z = zipfile.ZipFile(buffer)
    foo2 = z.open(z.infolist()[0])
    print(sys.getsizeof(foo2))
    line_counter = 0
    for _ in foo2:
        line_counter += 1
    print (line_counter)
    z.close()


if __name__ == '__main__':
    stream_zip_file()