Newbie requires help me on how to use the ZipFile module please.

[David Fraser]

Ian Cook wrote:
> Hi,
> Can someone PLEASE shed some light on using the ZipFile module
> correctly.
> I'm new to python so please excuse me if this is a 'dumb' question.
> 
> If I use mode='a' then what happens is the zip file just gets bigger
> and bigger as the SAME file is appended to the zipfile.
> 
> If I use mode='w' then what happens is the zip file is erased before
> adding files to it. Therefore I lose the files that were in the
> original file zipfile.
> 
> What I want is to use the ZipFile module to UPDATE an existing zip
> file, rather than append, or create a new zip file. The zip file then
> contains my original files and any updated files.
> 
> Does anyone know how this can be done with the Zipfile module?
> 
> This is a snippet of the code I have now..
> 
>                 try:
>                     zf = zipfile.ZipFile(zfname,mode='a')
>                 except:
>                     zf = zipfile.ZipFile(zfname,mode='w')
>                     
>                 for name in cutflist:
>                     fp = os.path.join(root,name)
>                     print "adding ",fp,"...",
>                     compresstype = zipfile.ZIP_DEFLATED
>                     if zipfile.is_zipfile(fp):
>                         compresstype = zipfile.ZIP_STORED
>                     zf.write(fp,compress_type=compresstype)
>                     print 'done.'
> 
> 
> 
> Thanks in advance.
> 
> Ian Cook

Curious, I posted a reply to the similar question you posted a week or 
two ago, but it doesn't show up in google groups... even though I got it 
from my nntp server...
So I'll post it again and Cc you :-)
Instead of attaching the file, you can get it here:
http://cvs.sourceforge.net/viewcvs.py/*checkout*/translate/src/translate/misc/zipfileext.py?rev=1.3

> 
> This is the module translate.misc.zipfileext from translate.sourceforge.net
> I use it to do updating of zip files (it adds some stuff on top of the normal zipfile class that I should really submit as a patch :-) )
> Can't recall all the details but I think even so its a bit hairy.
> For an example you could look at http://cvs.sourceforge.net/viewcvs.py/translate/src/translate/storage/xpi.py?rev=1.33&view=auto
> 
> The key method being this:
>   def overwritestr(self, zinfo_or_arcname, bytes):
>     """writes the string into the archive, overwriting the file if it exists..."""
>     if isinstance(zinfo_or_arcname, zipfile.ZipInfo):
>       filename = zinfo_or_arcname.filename
>     else:
>       filename = zinfo_or_arcname
>     if filename in self.NameToInfo:
>       self.delete(filename)
>     self.writestr(zinfo_or_arcname, bytes)
>     self.writeendrec()
> 
> Basically you need to delete existing files before you write to them if you want to replace them.
> 
> (This became more tricky) tricky as I was modifying zip files within zip files and trying to get them to store correctly, I ended up cloning the zip file objects, catching close events etc)
> Anyway maybe you can find something there that will help you.
> 
> David