…code, cg, electronics, 3d printing…

Originally posted on my Python Wiki

I was designing a UI for a PyGame program I am working on, and needed a way to pass a value defining a “row height” into the functions that rendered my text to the screen. Since the UI could change, I didn’t want to have to hard-code positions into each element, later to modify it and have to redo all the positions.
What I came up with was a simple class with a single usable attribute, called val. Through using properties, I’m able to control how the attr behavies at time time its value is queried:

class Row(object):
    # class to store the current row location in the UI
    # Each time it is called, it will increment its value
    def __init__(self, val):
        self._val = 0
        self.orig = val
    @property
    def val(self):
        self._val = self._val + self.orig
        return self._val
row = Row(16)

print row.val, row.val, row.val, row.val
# 16 32 48 64

Properties have getter, setter, and deleter methods, but the default is getter, which I used above. So as you can see, each time I call to print, it accesses the val property (via the getter), and updates the internal counter.
This is a PyGame code snippet showing it in use:

overlay.blit(bubble, (8, row.val))
overlay.blit(toggleText, (8, row.val))
overlay.blit(lmb, (8, row.val))

Rather than having to specify a Y value for the last arg of the tuple, I can simply pass in my object, and it passes out the current new position, based on how many times it was called before.

I have no doubt there is probably some slicker way in Python, but it’s what I came up with on the spot

This is the results of my latest efforts to learn PyGame using PyMunk, a Python wrapper around the Chipmunk 2D physics engine.  Eventually I hope to use this knowledge in a physics-based tank game, but right now, I’m just having fun ‘painting’ with the ‘bubbles’.  There’s no great magic going on in my opinion, just some weekend coding fun.

In a nutshell:

• You paint with “bubbles” on the canvas using the mouse.  It expects you have a 3-button mouse with a scroll wheel in the middle (because that’s what I have).  Since its physics based, the bubbles will push each other around, and none will be overlapping (if given time to settle).
• LMB-drag draws bubbles
• MMB-drag up\down: changes bubble size. Bigger bubbles get darker, smaller bubbles get lighter.
• RMB-drag up\down: change brush hue
• Mouse-wheel: change pressure of bubbles (number applied at once, from 1->10)
• ‘s’ will save ‘test.png’ in the install dir.

You can find the Python source here:

• http://www.akeric.com/python/bubblepaint/bubblePaint.001.py
• This was built with Python 2.6.2, PyGame 1.9.1, and PyMunk 0.8.4, so be sure to have all of those up to snuff.

And you can find a zipped Windows executable here:

• http://www.akeric.com/python/bubblepaint/BubblePaint001.zip

Future plans for this include:

• Shapes other than circles (square, triangle, random-polygon)
• Ability to enable gravity, and add static rigid bodies (more of a physics sandbox at that point)
• Images for the ‘bubbles’ rather than just solid color.
• The ability to ‘dry’ the canvas to allow for multiple layers of painting.
• A smarter way to save images.
• A toggleable overlay layer showing stats.
• Change the background color.
• User defined resolution.  Currently set to 768×768

But we’ll see how much of that happens, I have family coming into two for the next few weeks