On Fri, 2006-07-21 at 17:21 -0500, Ken McIvor wrote:
> On Jul 20, 2006, at 7:53 AM, Steven Chaplin wrote:
> >
> > However, print_figure() does not support writing to file objects in
> > different formats because it only takes a 'filename' argument and  
> > does not
> > have an argument to allow you to specify the format.
> 
> You can usually get the filename from the "name" attribute of a file- 
> like object.  Below is some untested pseudo-Python code that will use  
> the value of "format" if it's specified and will otherwise try to  
> pull the format from the file name.  You should be able to collapse  
> the nested if/else structure -- I've covered all four permutations  
> explicitly for clarity.
> 
> I'm too swamped to put a lot of time into this code/explanation, so  
> please let me know if this doesn't make any sense.
> 
> Ken
> 
> 
> def print_figure(self, fileOrString, format=None):
>       extension = None
> 
>       if is_file_like(fileOrString):
>               filename = getattr(fileobj, 'name', None)
>       else:
>               filename = fileOrString
> 
>       if filename is not None:
>               # get the extension and make it all lower-case
>               extension = os.path.splitext(filename, None)
> 
>       # figure out what the format is
>       if extension is None:
>               # no name file, so use format
>               if format is None:
>                       raise ValueError('you must specify a format')
>               else:
>                       pass # use the value of "format"                        
>         else:
>               # there's a name, but the format keyword overrides it
>               if format is None:
>                       # use the file extension
>                       format = extension
>               else:
>                       pass # use the value of "format"
> 
>       format = format.lower()
>       if format not in ('png', 'ps', 'svg'):
>               raise ValueError('invalid file format %r' % (format,))
> 
>       # At this point in the method, "format" is the requested file format.

The 'name' attribute is only useful sometimes:
 - it works for file objects (but only when the filename ends with a
format extension)
 - it does not work for sys.stdout, StringIO or cStringIO file-like
objects
I think an explicit 'format' argument is better than reading a 'name'
attribute which only works sometimes.

Steve

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