tmpfile and gzip combination problem

Question

I have problem with this code:

file = tempfile.TemporaryFile(mode='wrb')
file.write(base64.b64decode(data))
file.flush()
os.fsync(file)
# file.seek(0)
f = gzip.GzipFile(mode='rb', fileobj=file)
print f.read()

I dont know why it doesn't print out anything. If I uncomment file.seek then error occurs:

  File "/usr/lib/python2.5/gzip.py", line 263, in _read
    self._read_gzip_header()
  File "/usr/lib/python2.5/gzip.py", line 162, in _read_gzip_header
    magic = self.fileobj.read(2)
IOError: [Errno 9] Bad file descriptor

Just for information this version works fine:

x = open("test.gzip", 'wb')
x.write(base64.b64decode(data))
x.close()
f = gzip.GzipFile('test.gzip', 'rb')
print f.read()

EDIT: For wrb problem. It doesn't give me an error when initialize it. Python 2.5.2.

>>> t = tempfile.TemporaryFile(mode="wrb")
>>> t.write("test")
>>> t.seek(0)
>>> t.read()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IOError: [Errno 9] Bad file descriptor

Answer 1

'wrb' is not a valid mode.

This works fine:

import tempfile
import gzip

with tempfile.TemporaryFile(mode='w+b') as f:
    f.write(data.decode('base64'))
    f.flush()
    f.seek(0)
    gzf = gzip.GzipFile(mode='rb', fileobj=f)
    print gzf.read()

Answer 2

Some tips:

• You can't .seek(0) or .read() a gzip file in wrb mode or wb or w+b. GzipFile class __init__ set itself to READ or WRITE only by looking at the first character of wrb (set itself to WRITE for this case).
• When doing f = gzip.GzipFile(mode='rb', fileobj=file) your real file is file not f, I understood that after reading GzipFile class definition.

A working example for me was:

from tempfile import NamedTemporaryFile

import gzip


with NamedTemporaryFile(mode='w+b', delete=True, suffix='.txt.gz', prefix='f') as t_file:
    gzip_file = gzip.GzipFile(mode='wb', fileobj=t_file)
    gzip_file.write('SOMETHING HERE')
    gzip_file.close()
    t_file.seek(0)

    # Do something here with your t_file, maybe send it to an external storage or:
    print t_file.read()

I hope this can be useful for someone out there, took a lot of my time to make it work.