Writing then reading in-memory bytes (BytesIO) gives a blank result
PythonByteGzipBytesioPython Problem Overview
I wanted to try out the python BytesIO class.
As an experiment I tried writing to a zip file in memory, and then reading the bytes back out of that zip file. So instead of passing in a file-object to gzip, I pass in a BytesIO object. Here is the entire script:
from io import BytesIO
import gzip
# write bytes to zip file in memory
myio = BytesIO()
with gzip.GzipFile(fileobj=myio, mode='wb') as g:
g.write(b"does it work")
# read bytes from zip file in memory
with gzip.GzipFile(fileobj=myio, mode='rb') as g:
result = g.read()
print(result)
But it is returning an empty bytes object for result. This happens in both Python 2.7 and 3.4. What am I missing?
Python Solutions
Solution 1 - Python
You need to seek back to the beginning of the file after writing the initial in memory file...
myio.seek(0)
Solution 2 - Python
How about we write and read gzip content in the same context like this?
#!/usr/bin/env python
from io import BytesIO
import gzip
content = b"does it work"
# write bytes to zip file in memory
gzipped_content = None
with BytesIO() as myio:
with gzip.GzipFile(fileobj=myio, mode='wb') as g:
g.write(content)
gzipped_content = myio.getvalue()
print(gzipped_content)
print(content == gzip.decompress(gzipped_content))