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urllib2 FTP Weirdness

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  urllib2 FTP Weirdness Nick Cash <nick.cash@npcinternational.com> - 2013-01-23 20:07 +0000
    Re: urllib2 FTP Weirdness Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-01-24 11:41 +1100

#37501 — urllib2 FTP Weirdness

Python 2.7.3 on linux

This has me fairly stumped. It looks like
	urllib2.urlopen("ftp://some.ftp.site/path").read()
will either immediately return '' or hang indefinitely. But
	response = urllib2.urlopen("ftp://some.ftp.site/path")
	response.read()
works fine and returns what is expected. This is only an issue with urllib2, vanilla urllib doesn't do it.

The site I first noticed it on is private, but I can reproduce it with "ftp://ftp2.census.gov/".

I've tested the equivalent code on Python 3.2.3 and get the same results, except that one time I got a socket error (may have been a spurious network blip, though). 


I'm at a loss as to how that could even work differently. My only guess is that by not having a reference to the addinfourl response object, something important is getting garbage collected or closed... that seems like a stretch, though. Is this a urllib2 bug, or am I crazy?

-Nick Cash

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#37524

Nick Cash wrote:

> Python 2.7.3 on linux
> 
> This has me fairly stumped. It looks like
>     urllib2.urlopen("ftp://some.ftp.site/path").read()
> will either immediately return '' or hang indefinitely. But
>     response = urllib2.urlopen("ftp://some.ftp.site/path")
>     response.read()
> works fine and returns what is expected. This is only an issue with
> urllib2, vanilla urllib doesn't do it.
> 
> The site I first noticed it on is private, but I can reproduce it with
> "ftp://ftp2.census.gov/".

Then why not give that in your example, to make running your code
easier? :-)

I cannot reproduce the problem:


py> import urllib2
py> x = urllib2.urlopen("ftp://ftp2.census.gov/").read()
py> len(x)
5550


Works fine for me using Python 2.7.2 on Linux. I cannot see how the two
snippets you give could possibly be different. If you are using a proxy,
what happens if you bypass it?

If you can reproduce this at will, with and without proxy, with multiple
sites, then I suppose it is conceivable that it could be some sort of bug.
But I wouldn't bet on it.



-- 
Steven

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