> On 30 Sep 2019, at 09:55, Peter Otten <__pete...@web.de> wrote:
>
> DL Neil via Python-list wrote:
>
>> Should pathlib reflect changes it has made to the file-system?
>>
>>
>> Sample code, below, shows pathlib identifying a data-file and then
>> renaming it. Yet, after the rename operation, pathlib doesn't recognise
>> its own change; whereas the file system does/proves the change was
>> actioned.
>>
>>
>> $ touch before.file
>> $ python3
>> Python 3.7.4 (default, Jul 9 2019, 16:48:28)
>> [GCC 8.3.1 20190223 (Red Hat 8.3.1-2)] on linux
>> Type "help", "copyright", "credits" or "license" for more information.
>>>>> import pathlib
>>>>> p = pathlib.Path( "before.file" )
>>>>> p
>> PosixPath('before.file')
>>>>> p.name
>> 'before.file'
>>>>> p.rename( "after.file" )
>>>>> p.name
>> 'before.file'
>>>>> exit()
>> $ ls -lah after*
>> -rw-rw-r--. 1 dn dn 0 Sep 30 16:05 after.file
>> $ ls -lah before*
>> ls: cannot access 'before*': No such file or directory
>>
>>
>> I would expect pathlib to keep track of changes it has made. Any
>> ideas/good reasons why/why not?
>> NB "name" is a r/o attribute.
>
> This is certainly not a backwards-compatible change. Consider:
>
> p = pathlib.Path("data.txt")
> p.rename("data.txt.bak")
> with p.open("w") as f:
> f.write("new stuff") # oops, we are overwriting the backup
>
> Also, it will not necessarily be as obvious as in the above example.
> Everywhere you write
>
> p = q
>
> you produce an occasion to unexpectedly change a file reference. Generally,
> it's easier to reason about immutable objects.
>
> What might be helpful would be to return a new Path object
>
> renamed = original.rename(...)
I do not think this is useful as in my code I will already have a path object to
use as the rename target.
src = pathlib.Path('/source/data.txt')
dst = pathlib.Path('/backup/data.bak')
src.rename( dst )
print( 'Renamed %s to %s' % (src, dst) )
>
> but as I'm not a pathlib user I have no idea what the use-it to throw-it-
> away ratio would be.
Barry
>
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