RetroSearch Browse

Sun Jun 29 12:52:40 CEST 2014 · https://mail.python.org/pipermail/python-dev/2014-June/135258.html

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

Home - News ( United States | United Kingdom | Italy | Germany ) - Football scores

Showing content from https://mail.python.org/pipermail/python-dev/2014-June/135258.html below:

[Python-Dev] PEP 471 -- os.scandir() function -- a better and faster directory iterator