I have a python application that relies on a file that is downloaded by a client from a website.
The website is not under my control and has no API to check for a "latest version" of the file.
Is there a simple way to access the file (in python) via a URL and check it's date (or size) without having to download it to the clients machine each time?
update: Thanks to those who mentioned the"last-modified" date.  This is the correct parameter to look at.
I guess I didn't state the question well enough.  How do I do this from a python script?  I want to application to check the file and then download it if (last-modified date < current file date).
Take into account that 'last-modified' may not be present:

>>> from urllib import urlopen
>>> f=urlopen('http://google.com/')
>>> i=f.info()
>>> i.keys()
['set-cookie', 'expires', 'server', 'connection', 'cache-control', 'date', 'content-type']
>>> i.getdate('date')
(2009, 1, 10, 16, 17, 8, 0, 1, 0)
>>> i.getheader('date')
'Sat, 10 Jan 2009 16:17:08 GMT'
>>> i.getdate('last-modified')
>>>

Now you can compare:

if (i.getdate('last-modified') or i.getheader('date')) > current_file_date:
  open('file', 'w').write(f.read())
How can I get the created date of a file on the web (with Python)?