Wednesday, April 01, 2015

You gotta love a good library

The Columbus Metropolitan Library is arguably one of the best libraries in the nation.  I use it so much I have had my library card memorized for over 25 years.  The idea that there is information and services there at my fingertips any time I want is fantastic.  I was thinking about this yesterday when I started pulling functions out of PyVrGeom().  Libraries (modules) can be everything from little bits of code snippets that you want to reuse over and over to complex collections of classes that you could only dream up but never realistically code yourself. 

For example PyVrGeom is just a collection of math that some would find easy enough to code, but why do so when somebody has done the heavy lifting and offers you the calls to do it with some preexisting code.  In this case very professionally created and presented, but it is just as easy to hack together some snippets that just save you typing.  For example when I was working on a KML export routine I didn't need to learn something complex and universal (which libs probably exist), I just knew what it looked like and wanted to replicate those entities by passing along a few basic parameters.  In this case I slapped together some code to create the KML entities, but at the same time the coordinates needed to be in geodetic coordinates so I had to grab a projection library that someone way sharper than me had already put together. Then it struck me that a KMZ is just a file zipped using the standard algorithms so if I import that one I can just as easily write both KML and KMZ files.

I'm not going to offer any code this time just another reminder that there are some good reasons to install python if you are going to do some scripting.  Here are some of the libraries that I really enjoy and use often.

pyproj - for converting local coordinates to global (or from one to another).
liblas - for all things LiDAR related.
zipfile - for reading and writing compressed files.
xlrd/xlwt - for directly reading and writing Excel spreadsheets.

Along with some of the standard system libraries that you can find a million uses for like sys, os, time, and math.

And here is a tip I'll add for free, check out

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For anyone interested in trying VrPython for the first time or if you are early in the game, I suggest going to the earliest posts and working forward. I use VrPython every day for many wonderful things, needless to say it will change and could potentially damage a file. Any risk associated with using VrPython or any code or scripts mentioned here lies solely with the end user.

The "Personal VrPython page" in the link section will contain many code examples and an organized table of contents to this blog in a fairly un-attractive (for now) form.