Saturday, January 19, 2008

More power and removing an option

One of the neat features of Crunchy, suggested to me by Andrew Dalke at Pycon 2007, is its ability to dynamically display images that are generated by some Python code. The example given in the Crunchy distribution uses matplotlib. However, the way this is done is slightly cumbersome. First, some pre-existing vlam (very little added markup) must already have been added to an html page, specifying the name of the image (e.g. foo.png) to be displayed. This special vlam will result in an editor appearing on the page together with two buttons (one to execute the code, the other to load the image). Second, the Python code must be such that an image will be generated with that name. By default, the image is saved in and retrieved from a special Crunchy temp directory.

While the approach used works, it does also mean that images can't be generated and displayed using a simple Python interpreter, nor can they be displayed from an arbitrary location. At least that was the case until now.

Prompted by a suggestion from Johannes, I wrote a very simple module whose core consists of only 7 Python statements, and which does away entirely with the cumbersome vlam image file option. Images can now be loaded and displayed from anywhere using two lines of code:

import image_display, [width=400, height=400])

And by anywhere, I mean from any interactive Python element (interpreter, editor),
and using any image source (local images and images on the web), like'')

Furthermore, one can use this approach to create a "slide show" by alternating and time.sleep().

Since there is no more need to use the old image_file option, it will be removed in the next Crunchy release. I may have to give some more thoughts to the API for this new option (e.g. is there a better name than image_display? Should I add a function for a slide show, giving a list of images and a time delay? etc.); suggestions are welcome.

1 comment:

Paddy3118 said...

If Crunchy on Python 3 is robust at Python 3 launch time it would be great if you could get a number of Python 3 reviewers to review via crunchy applied to the tutorial.

- Paddy.