[reportlab-users] isinstance(val, file)

[Carl Karsten]

This is not really a reportlab problem, but close enough.

How can I test that the file to be passed to canvas.Canvas(buffer) is really a 
file type object that can be written to?  I am trying to work with a wrapper 
that looks like this:

     val = StringIO()
...

                 if isinstance(val, file) or True:
                         self._outputFile = val
                 else:
                         s = os.path.split(val)
...
     p = canvas.Canvas(val)

Val isn't a file, so it hits the else and blows.

I could check for isinstance(val,str) but was would feel better if there was a 
sure fire way to verify that what was going to be passed to canvas.Canvas(val) 
was going to work.

Carl K