[Python-Dev] os.walk() silently ignores errors

[Harri Pasanen]

On Tuesday 13 May 2003 15:51, Guido van Rossum wrote:
> > I've just noticed that os.walk() silently skips unreadable
> > directories.  I think this is surprising behaviour, which at
> > least should be documented (there is a comment explaining this is
> > source, but nothing in the doc string).  Is it too late to add an
> > optional callback argument to handle unreadable directories, so
> > the caller could log them, raise an exception or whatever?  I
> > think the default behaviour should still be to silently ignore
> > them, but it would be nice to have a way to override it.
>
> Ignoring is definitely the right thing to do by default, as
> otherwise the existence of a single unreadable directory would
> cause your entire walk to fail.  What's your use case for wanting
> to do something else?

Sometimes I'm looking for something in a files in directory tree, 
forgetting I don't have access permissions to a particular 
subdirectory by default.  So the search can silently fail, and I'm 
left with the wrong idea that what I was looking is not there.

Ideally, I'd like the possibility have my script remind me to login as 
root prior to running it.
 
I know I could do some defensive programming in the walker function to 
go around this, but I this would likely imply more stat calls and 
impact performance. 

I've been bitten by this a couple of times, so I thought I'd pipe in.  

-Harri