"Frank Millman" <[EMAIL PROTECTED]> ha scritto nel messaggio news:[EMAIL PROTECTED] > Hi all > > I need to generate potentially large reports from a database, and I > want to offer the option of print preview before actually printing > (using wxPython). I figure that the best way to achieve this is to > write the report to a temporary file, or more likely to a temporary > directory with a separate file for each page. I can use that for > previewing and for printing, and then delete the file/directory. > > There seems to be a few ways to achieve this, and I am not sure of the > best way. > > 1. I can call tempfile.TemporaryFile() for each file required. > > 2. I can call tempfile.mkdtemp() to create a temporary directory, and > create each file manually. > > 3. I can call os.tmpfile() for each file required. > > After creating the files, I need to re-read them, either one at a time > in sequence (if printing), or any one at random (if previewing a > particular page). This makes me lean towards method 2. > > With this method, I create the files manually, so I can name them > according to their page numbers, which makes it easy to open and close > them as required. The other two methods return open file objects, so > it seems that I cannot close them, as there would be no means of > accessing their contents subsequently. Therefore I would have to > maintain a list of open file objects, use indexing to retrieve a > particular page, and then perform seek(0) before I could read it. A > slight downside of method 2 is that I have to delete the files and the > directory manually when I have finished. > > I have two additional questions regarding method 3. > > Firstly, I am not sure how it works. The docs say that the file has no > directory entries associated with it, and it will be automatically > deleted when there are no file descriptors for the file. What does > this mean? Does it create a physical file, or is it stored in memory? > If the latter, could I run into memory problems if I create a report > with hundreds of pages? > > Secondly, I can create the file using FC3 (Python 2.4), but if I try > on Windows 2000 (Python 2.4) I get the message 'OSError: Permission > denied', even though I am a member of the Administrators group. > > Any advice on the best approach for this will be much appreciated. > > Frank Millman
Why create an intermediate file to preview with wxPython? I would just preview the data with wx and keep it inside your application. If you want to print it just print... avoid temp file creation if it's not necessary... :) F.P. -- http://mail.python.org/mailman/listinfo/python-list
