[Tutor] Fwd: Is this possible and should it be done?
-- Forwarded message -- From: wolfrage8...@gmail.com wolfrage8...@gmail.com Date: Mon, May 21, 2012 at 2:16 PM Subject: Re: [Tutor] Is this possible and should it be done? To: Steven D'Aprano st...@pearwood.info Thank you for the information. Sorry if I implied I wanted to re-invent the wheel but actually this feedback is exactly what I was looking for. I wanted to know existing methods to do just such operations. Also good point about the file browsers the only limitation to them is how much they understand the format. So since tar looks like an excellent option for what I want to do, I have another question before I begin my research. Do you already know if any of these formats offer file locking with in them, ;et me say that better. Can I open a, as example, tar file and lock a file with in it, with out locking the entire tar archive? Just asking if you already know if this is possible? Thank you again for the information! SNIPED ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Fwd: Is this possible and should it be done?
On 21/05/12 15:23, wolfrage8...@gmail.com wrote: if any of these formats offer file locking with in them, ;et me say that better. Can I open a, as example, tar file and lock a file with in it, with out locking the entire tar archive? No and you probably shouldn't. If two users are accessing the same file at once and one of them is modifying it (writing) while the other is trying to read it bad things are very likely to happen. Remember that these virtual files inside the tar file(say) are really just blocks of data within a single file. If you want to try modifying blocks inside a single store you will be better with a database. But that's not usually a single file (Access, SQLite etc excepted). Actually SQLite might do what you want by locking at the table row level, I haven't checked. You would need a single table of BLOB records where each BLOB represented a virtual file... Version control tools like CVS and SVN don't quite fit your needs either since they use multiple files not a single file. Although they do usually store all the historic versions of each file in one. So if it is really only historic data you need CVS, SVN, RCS etc may work. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Fwd: Is this possible and should it be done?
On 05/21/2012 07:24 PM, Alan Gauld wrote: On 21/05/12 15:23, wolfrage8...@gmail.com wrote: if any of these formats offer file locking with in them, ;et me say that better. Can I open a, as example, tar file and lock a file with in it, with out locking the entire tar archive? No and you probably shouldn't. If two users are accessing the same file at once and one of them is modifying it (writing) while the other is trying to read it bad things are very likely to happen. Remember that these virtual files inside the tar file(say) are really just blocks of data within a single file. If you want to try modifying blocks inside a single store you will be better with a database. But that's not usually a single file (Access, SQLite etc excepted). Actually SQLite might do what you want by locking at the table row level, I haven't checked. You would need a single table of BLOB records where each BLOB represented a virtual file... Very interesting idea, I have actually used a SQLite file in this way before, not sure why I did not think of that possibility. SQLite's BLOB could be the perfect already created solution. Thank you all for your inputs. Version control tools like CVS and SVN don't quite fit your needs either since they use multiple files not a single file. Although they do usually store all the historic versions of each file in one. So if it is really only historic data you need CVS, SVN, RCS etc may work. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
