Paul Moore wrote:
I was just reviewing the patch at http://python.org/sf/941486, which proposes adding a new 'lexists()' function to os.path. This function would return True for dangling symbolic links, unlike os.path.exists() which returns False. One could use 'os.path.islink(path) or os.path.exists()' as well, but that's two stat calls instead of one.
As an alternative, would there be any value in cacheing the last stat result? In a sequence like this, with multiple calls for the same argument, many stat calls would be replaced by one. And it's likely that the checking overhead on cache misses would be minimal compared to the cost of the stat call, so it's an overall win.
Hi Paul, you will never know how long the cached result is true. Files on disk can change outside your python script.... I doubt that we can find a good expire time for the caching? Someone will come up with an application in which this caching will give wrong results... If someone knows what he does and likes efficient programming he can cache the result of os.stat() himself and work with that. (Like this lexists() function is programmed internally...) My personal opinion: +0.5 for os.lexists() [it's useful, but we can also live without it...] -1 for a stat cache in os.*. Cheers, Tino