The following code create circular references in python:
>>> aRef = [] >>> aRef.append(aRef) >>> print aRef [[...]]
This creates a list object referred by a variable named “aRef”. the first element in the list object is a reference to itself. In this case, the “del aRef” dereference aRef to the list object. However, the reference count of the list object does not decrease to zero and the list object is not garbage collected, since the list object still refers to itself. In this case, the garbage collector in Python will periodically check if such circular references exist and the interpreter will collect them. The following is an example to manually collect the space used by circular referenced objects.
>>> import gc >>> gc.collect() 0 >>> del aRef >>> gc.collect() 1 >>> gc.collect() 0
Maker Faire 2007
Jun 24
Posted by Jason Chin in comment, misc | No Comments
I went to Maker Faire yesterday. I have been a Make magazine subscriber since its debut and I like to hack and make things. Although I have been working some project for my work (in systems biology) last year very hard to a degree that I did not feel to do anything anymore. Since the project is near the end and I am in a position trying to seek new opportunities in my life, it might be a good time to revive some hacker/maker sprit in my heart. So, I could not miss the second Maker Faire,.
My families and I arrived the faire around 10 o’clock. We first spent some time on the Robot Pavilion to see quite a few different interesting robot. Some of them are quite extraordinary, e.g., robots driven by steam engine, self-balancing robot, and home-made Segway, etc.
Although there was a schedule for different presentation and demonstration, with a less than two years old toddler, we were just doing random walk in the faire ground afterward.
The largest Maker demonstration was at ___. Half of the hall was for “Maker” and half of the hall was for “Crafter”. Joy was joking about that most women can stay in the crafter part and most of men can stay in the maker part and this made the “Maker/Crafter Faire” as a great event for family. One can found some of those projects in Make demonstrated in the maker part. There was also a DIY lab to make a “Ybox” provided by Yahoo as sponsor. It was interesting to see that Yahoo seemed putting more effort for this “Maker” event. Compared to Yahoo, Google only put a few computers demonstrating Sketcher. On the other hand, Microsoft did demonstrate some of their cool lab technologies. I talked to a engineer showing me their new web mash-up tools, popfly. It seemed quite interesting, but I had yet to tried it out by myself. Well, at least, my daughter liked their “ducks”.
In the main Make demonstration, what I found quite interesting was the 3D Metal sculptures by Bathsheba. This was my first time to see the results of a 3D printer using metal as the material. It just is amazing to see new technology combining the beauty of math and science. Although I had seen some of the mathematical surfaces on a computer screen, it was just more exciting to see them as “real things”. It was very tempting to buy one of the sculptures and I would probably eventually order one sometime. Or, make one myself for myself in the future. I think I can do it by joining the TechShop and I can use their 3D ABS printer to construct some 3D sculptures too.
There were also all kind of bikes and human powered machines and quite a few DIY activities for kids and adults. Well, my one-and-half years old daughter, Emily was still too small for most of those activities but she seemed like the faire a lot. Oh, she liked the Wii remote controlled RC cars. Ha, this might be a good excuse to buy a Wii, for her and for me (to hack).
Later on, I found the booth Sun demonstrating their Java-power embedding system developing gadget “Sunspot”. The “Sunspot” seemed a cute and powerful little machine for all sorts of purposes, but it was a little bit expansive.
Overall, my families and I had a fun and inspiring day. All I hope is that I will be able to get time to develop some cool projects myself in the near future.
What are interesting:
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3D Metal sculptures by Bathsheba — exploring how math, science and sculpture meet (web site). ProMetal is the company which make the sculptures by a technology that can “print” metal layer by layer.
TechShop — A club which the members can use their machines for prototyping and DIY. The membership costs $100 per month. I find it is very attractive. If I decide to make something cool, no doubt I will get a membership and learn to use all cool machines they have. They have a 3D ABS printer (from Scicon?) that can be used for fast prototype.
Lots of robots.
Sunspot
Popfly
Moto labs
STL file format for 3D sculpture/prototype.
Pick the nose!!
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Yahoo, Ybox.tv
puzzle maker
some pictures
Tags: misc