How can I create a GzipFile instance from the “file-like object” that urllib.urlopen() returns?

Question

I’m playing around with the Stack Overflow API using Python. I’m trying to decode the gzipped responses that the API gives.

import urllib, gzip

url = urllib.urlopen('http://api.stackoverflow.com/1.0/badges/name')
gzip.GzipFile(fileobj=url).read()

According to the urllib2 documentation, urlopen “returns a file-like object”.

However, when I run read() on the GzipFile object I’ve created using it, I get this error:

AttributeError: addinfourl instance has no attribute 'tell'

As far as I can tell, this is coming from the object returned by urlopen.

It doesn’t appear to have seek either, as I get an error when I do this:

url.read()
url.seek(0)

What exactly is this object, and how do I create a functioning GzipFile instance from it?

Answer 1

The urlopen docs list the supported methods of the object that is returned. I recommend wrapping the object in another class that supports the methods that gzip expects.

Other option: call the read method of the response object and put the result in a StringIO object (which should support all methods that gzip expects). This maybe a little more expensive though.

E.g.

import gzip
import json
import StringIO
import urllib

url = urllib.urlopen('http://api.stackoverflow.com/1.0/badges/name')
url_f = StringIO.StringIO(url.read())
g = gzip.GzipFile(fileobj=url_f)
j = json.load(g)

Answer 2

import urllib2
import json
import gzip
import io

url='http://api.stackoverflow.com/1.0/badges/name'
page=urllib2.urlopen(url)
gzip_filehandle=gzip.GzipFile(fileobj=io.BytesIO(page.read()))
json_data=json.loads(gzip_filehandle.read())
print(json_data)

io.BytesIO is for Python2.6+. For older versions of Python, you could use cStringIO.StringIO.

Answer 3

Here is a new update for @stefanw's answer, to whom that might think it too expensive to use that much memory.

Thanks to this article(https://www.enricozini.org/blog/2011/cazzeggio/python-gzip/, it explains why gzip doesn't work), the solution is to use Python3.

import urllib.request
import gzip

response = urllib.request.urlopen('http://api.stackoverflow.com/1.0/badges/name')
with gzip.GzipFile(fileobj=response) as f:
    for line in f:
        print(line)