如何在没有数据库的情况下使用python Transaction？

Question

I have two line in my code which first one is os.unlink and second one is os.symlink . like :

os.unlink(path)
os.symlink(new_path)

The sequence should not be change, The problem is, some times it unlink a file (in other word it remove it's shortcut) but second line could not create symbolic link (do to some addressing issue).

My question is: Is there any all or non transaction tool like the one we have in database, to do both line or non ?

Answer 1

you could try this:

import os

linkname = '/tmp/test.lnk'
orig_target = os.path.realpath(linkname)
os.unlink(linkname)
try:
    os.symlink(new_target, linkname)
except:
    os.symlink(orig_target, linkname)

maybe check what exceptions can occur and only catch the ones that are relevant.

Answer 2

Strictly speaking it is not possible unless you use Transactional filesystem like TxF ( https://en.wikipedia.org/wiki/Transactional_NTFS ) because nothing prevents your machine from poweroff between two commands.

I can see 2 ways here:

1) Switch to Database

2) Check all conditions before unlinking. What prevents you from symlinking?