Decode gzip compressed and base64 encoded data to

Question

Trying to decode gzip compressed and base64 encoded data to a readable format in Python3.4.

import base64
import zlib

original_data = '...jU2X0NCQ19TSEEAAAABAAA='     #Data cut short.

decoded64 = base64.b64decode(original_data)      #format:b'\x16xe\x94...\xae\x9a\...'
final_decoded = zlib.decompress(decoded64)
print(final_decoded)

Been getting: "Error -2 while preparing to decompress data: inconsistent stream state." Not sure what I'm doing wrong.

Answer 1

zlib successfully decompresses data that it has compressed previously:

>>> data = b'data'
>>> import zlib
>>> compressed = zlib.compress(data)
>>> import base64
>>> original_data = base64.b64encode(compressed).decode()
>>> zlib.decompress(base64.b64decode(original_data))
b'data'

zlib fails to decompress (with the default settings) gzip data:

>>> import gzip
>>> gzipped_data = base64.b64encode(gzip.compress(data)).decode()
>>> gzipped_data != original_data
True
>>> print(zlib.decompress(base64.b64decode(gzipped_data)))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
zlib.error: Error -3 while decompressing data: incorrect header check
>>> gzip.decompress(base64.b64decode(gzipped_data))
b'data'

Answer 2

I had the same problem and solve it this way:

from zipfile import ZipFile
from tempfile import SpooledTemporaryFile
import base64
decoded_base64 = base64.b64decode(base64_zip)
with SpooledTemporaryFile() as tmp:
    tmp.write(decoded_base64)
    archive = ZipFile(tmp, 'r')
    for file in archive.filelist:
        content = archive.read(file.filename)
        print("The file %s have the content %s" % (file.filename, content))

Using this your code doesn't write a file, I tested. Is very useful because you can easily read a file inside a zip file, previously received by rest for example.