compression - Python ungzipping stream of bytes?

Question

Here is the situation:

• I get gzipped xml documents from Amazon S3

    import boto
    from boto.s3.connection import S3Connection
    from boto.s3.key import Key
    conn = S3Connection('access Id', 'secret access key')
    b = conn.get_bucket('mydev.myorg')
    k = Key(b)
    k.key('documents/document.xml.gz')
  

• I read them in file as

    import gzip
    f = open('/tmp/p', 'w')
    k.get_file(f)
    f.close()
    r = gzip.open('/tmp/p', 'rb')
    file_content = r.read()
    r.close()
  

Question

How can I ungzip the streams directly and read the contents?

I do not want to create temp files, they don't look good.

Answer 1

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