On Sat, Jun 28, 2014 at 03:55:00PM -0400, Ben Hoyt wrote:
> Re is_dir etc being properties rather than methods:
[...]
> The problem with this is that properties "look free", they look just
> like attribute access, so you wouldn't normally handle exceptions when
> accessing them. But .lstat() and .is_dir() etc may do an OS call, so
> if you're needing to be careful with error handling, you may want to
> handle errors on them. Hence I think it's best practice to make them
> functions().
I think this one could go either way. Methods look like they actually
re-test the value each time you call it. I can easily see people not
realising that the value is cached and writing code like this toy
example:
# Detect a file change.
t = the_file.lstat().st_mtime
while the_file.lstat().st_mtime == t:
sleep(0.1)
print("Changed!")
I know that's not the best way to detect file changes, but I'm sure
people will do something like that and not realise that the call to
lstat is cached.
Personally, I would prefer a property. If I forget to wrap a call in a
try...except, it will fail hard and I will get an exception. But with a
method call, the failure is silent and I keep getting the cached result.
Speaking of caching, is there a way to freshen the cached values?
--
Steven
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