[mod_python] matplotlib and sys.stdout[.write()] <> req[.write()]

>>>>> "Adrian" == Adrian Immler <mod_python-maillist at uebergeek.de> writes:

    Adrian>   File "/www/uebergeek.de/htdocs/music/test.py", line 45,
    Adrian> in test canvas.print_figure(req)

    Adrian>   File
    Adrian> "/usr/lib/python2.4/site-packages/matplotlib/backends/backend_agg.py",
    Adrian> line 383, in print_figure basename, ext =
    Adrian> os.path.splitext(filename)

    Adrian>   File "/usr/lib/python2.4/posixpath.py", line 92, in
    Adrian> splitext i = p.rfind('.')

    Adrian> AttributeError: 'mp_request' object has no attribute
    Adrian> 'rfind'

    Adrian> so it is nearly the same error. now my question is:

    Adrian> how can i create a png file with matplotlib and send it to
    Adrian> the client without saving the file to harddisk and send
    Adrian> that one.

    Adrian> thanks in advance !



    Adrian> p.s. yes i know that the content_type('image/png') is
    Adrian> missing in the above example ...


It looks like mod_python is doing something funny with sys.stdout,
because I can run your script in as a standalone python script

    import sys
    import matplotlib
    matplotlib.use('Agg')
    from matplotlib.backends.backend_agg import FigureCanvasAgg as FigureCanvas
    from matplotlib.figure import Figure

    fig = Figure()
    canvas = FigureCanvas(fig)
    ax = fig.add_subplot(111)
    ax.plot([1,2,3])
    ax.set_title('hi mom')
    ax.grid(True)
    ax.set_xlabel('time')
    ax.set_ylabel('volts')
    canvas.print_figure(sys.stdout)

Run with 

 > python test.py > test.png

Everything works as it should.

The relevant code in lib/matplotlib/backends/backend_agg.py around
line 377 is

        if  isinstance(filename, file):
            # assume png and write to fileobject
            self.renderer._renderer.write_png(filename)
            #pass
        else:
            # take a look at the extension and choose the print handler
            basename, ext = os.path.splitext(filename)
            if not len(ext):
                ext = '.png'

You want to be in the first part of this conditional, ie, you want the
call to 

    self.renderer._renderer.write_png(filename).

Apparently the isinstance(filename, file) test is failing under
modpython and working under normal python.  Anyone know why, or what
would be a more appropriate test for a file object under modpython

JDH