Unzip Files

[Tim Chase]

> I am new to python, so please don't attack me if this question is easy
> or basic.  How can I go about extracting the contents of a zip file to
> the same directory?  Can I extend this question to a zip file that
> sits on the internet?

While the ZipFile object can take a file-like object, it looks 
like it expects to at least be able to seek() on that 
file-object.  The object you get back from a urlopen() call 
doesn't offer a seek(), so you can't directly use this object.

As such, you'd have to (1) download the remote .zip locally or 
(2) create your own urlopener (a'la urllib) that has a seek() 
method and uses HTTP Content-Range[1] if the server supports it. 
  Method #1 is fairly easy (especially if the file fits entirely 
within memory) but assumes the file isn't gargantuan because 
you're slurping the entire file over the network.  Method #2 
requires much crazier hacking skills but could produce serious 
gains if your file was mammoth.

> Point being I need to work with the files inside the zipped file, and
> there are times when the file is already on my computer, and their
> others where the datafile sits on the Internet.

I'd create a wrapper that checks if the passed "filename" is a 
URL or a filename.  If it's not a local file, download it to a 
local tempfile, and then proceed with that file the same as with 
the local file, only optionally deleting it when done.

Since the ZipFile can take any file-like that allows for seek(), 
memory permitting, you can even read the web-content into a 
cStringIO object without having to touch your filesystem.

-tkc

[1]
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.16