Going the other direction is complicated by the fact that service request and response objects, which walk and talk like messages, aren’t actually messages. So populating a call to a service and reading the response requires specifying some code in advance that knows how to translate a service response into a proper message. You can’t use the response object as a topic message type directly since it’s not actually a visible message type and roscore will complain that it can’t find the message definition.

In general, it would be nice if services and messages could be specified dynamically, but I suspect that the performance requirements of serialization require that these be specified in advance and compiled.

Now for some pointless musing about what’s really going on. The point of SOPA/PIPA is not to combat piracy in the sense that most people understand it. I finally figured out what’s going on when I realized that for people supporting SOPA, the biggest internet pirate isn’t some torrent site like The Pirate Bay, it’s Google.

The “secret” plan isn’t to censor the internet, or take down pirate sites, or throw Google/Facebook/Wikipedia offline. The goal is to maximize revenue for existing intellectual property and the method is straightforward crony capitalism.

1. Finance political campaigns.
2. Lobby for a laws that provide leverage.
3. Negotiate lucrative blanket license agreements with major players.

Nobody in Hollywood cares about real piracy because most smart people realize that there isn’t a lot of money there. The people who use sites with pirated content aren’t easily converted into paying customers. This law will do nothing to shut down sites like The Pirate Bay or prevent people from using them. Instead, this law is aimed squarely at more lucrative targets, with the intention of facilitating a transfer of wealth from companies like Google/Facebook/Twitter to associations of content creators.

My prediction: If SOPA/PIPA pass then some form of step 3 won’t be far behind.

Running this with

python ipickle.py

gives:

stober[~/Dropbox/workspace/gist]{laptop}$ python ipickle.py
<__main__.A instance at 0x10cc37bd8>

Running the same thing with IPython

ipython ipickle.py

produces decidedly different output:

 
stober[~/Dropbox/workspace/gist]{laptop}$ ipython ipickle.py 
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
/Users/stober/Dropbox/workspace/gist/ipickle.py in <module>()
     16     pickle.dump(A(), open("A.pck","w"))
     17 
---> 18     a = pickle.load(open("A.pck"))
     19     print a
 
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.pyc in load(file)
   1376 
   1377 def load(file):
-> 1378     return Unpickler(file).load()
   1379 
   1380 def loads(str):
 
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.pyc in load(self)
    856             while 1:
    857                 key = read(1)
--> 858                 dispatch[key](self)
    859         except _Stop, stopinst:
    860             return stopinst.value
 
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.pyc in load_inst(self)
   1067         module = self.readline()[:-1]
   1068         name = self.readline()[:-1]
-> 1069         klass = self.find_class(module, name)
   1070         self._instantiate(klass, self.marker())
   1071     dispatch[INST] = load_inst
 
/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.pyc in find_class(self, module, name)
   1124         __import__(module)
   1125         mod = sys.modules[module]
-> 1126         klass = getattr(mod, name)
   1127         return klass
   1128 
 
AttributeError: 'FakeModule' object has no attribute 'A'

It turns out you’ll never generate two of the same SHA1 hashes. The chances are miniscule. There’s room for all kinds of flowery comparisons like: You’d have to generate more hash codes than the number of stars in the universe before you’d get two of the same!

But my favorite is from Pro Git: “A higher probability exists that every member of your programming team will be attacked and killed by wolves in unrelated incidents on the same night.”

Since I’m sort of disorganized, I’ll often start working on a new feature and then remember that I’m working on master and not on a separate branch. Provided I haven’t made any commits, there’s an easy way to form a new branch out of the local changes — git stash; git stash branch [branchname].

3. Be important enough to have an email problem.

One strange trend is for people (usually from an engineering background) to complain on blogs and things about having an email problem. The phrase “email is broken” is usually mentioned.

What’s broken is the engineering mindset. Chances are if you are important enough to have an email problem, you are important enough to have an assistant devoted to prioritizing your email. Weird that this obvious solution isn’t adopted more often. (Maybe it is — not every successful person with a blog complains about email.) Instead we’re subjected to endless blog posts. I may never be important enough to have an email problem, much less an assistant of any kind, but for some reason the endless complaining about email online from people that are really rubs me the wrong way.

Then I remembered the setdefault method and was able to create a more concise function:

Of course if your dictionary is 1-1, you probably don’t want to introduce sets into the reverse version, so I created a function that composes nicely with the previous function:

Pywebcam would have been a (very) niche tool with only a small long tail audience, but half the traffic to this blog is a result of a niche tool fixing a temporary bug in version 1.0 of the OpenCV Python bindings. I did end up hosting some code that I used for pages I wrote in a previous version of this blog, meant as simple Pythonic implementations of interesting machine learning algorithms. That project, pyrouette, is being migrated to Bitbucket after I neglected the public repository while doing a ton of development on my own private repo.

Here too, I think the design of the Google Code service is built around dissuading single developers on these kinds of long tail projects from ever updating their public repositories. This combined with the general lack of control over what and how things were presented made the service unusable for me. (No private repositories; Forced to choose a license upfront; No ability to embed code on my blog; Even deleting projects is dicey.) My code languished, my blogging about my code languished, and now I’m going to try a different service.

I may eventually end up on Github with the cool kids, but for now I’m sticking with Mercurial. The devil you know and all that.

Today I made use of pdftk to combine a bunch of separate PDF documents:

pdftk A.pdf B.pdf C.pdf cat output merged.pdf

My PDF included an image file that was inflating the size past what would be appropriate to email. What is the etiquette on emailing big files these days anyway? I always try to keep things close to or less than 1mb, but I imagine less than 10mb must be closer to the norm.

pdftk is supposed to also have a compress/decompress option, but I could not figure out the syntax so I went with the always trusty but somewhat opaque ghostscript option.

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf

1. Hard to see how the mechanized adaptive exercises would transfer to non-STEM areas of basic knowledge.
2. Based on what little I know, problems in education are too complex for these kinds of solutions.
3. The people at TED are just totally blinded by privilege.
4. Also, there’s a bit of this going on.
5. Better education will probably require real public engagement, not the ad hoc interest of a philanthropist for the latest technological fad.