Sunday, September 27, 2015

Flattening Python Code with "continue"

Flat code is better than nested.  It's more readable, easier to update, and easier to debug.  All of the linux kernel source code uses 8-space indents because, as I've seen it explained by Linus, if you can't use enough indents with 8-space, you have too many indents and need to refactor your code so it's more simple.

I do some data analysis type stuff at work fairly often.  Sometimes I'll have a half-dozen conditional statements to satisfy in a loop where I'm ticking over rows of data.  Using the "continue" statement is a really simple way to keep code flat and manageable.

Bad form would be like this:
for row in my_data:
    if row[val] == 'blah':
        if row[val2] == 'test':
            if row[val3]:
                yield row

Better would be like this:
for row in my_data:
    if row[val] != 'blah':
    if row[val2] != 'test':
    if row[val3]:
        yield row

Monday, August 31, 2015

Raspberry Pi Projects

For years, I've been listening to people talk about the projects that they want to use the Raspberry Pi boards for.  I've never really had any good ideas... until now!

Automotive Data-Logger

This would include a dash cam and a reverse cam and would be a fairly involved project.  The RPi is a great candidate for this project because of it's low power requirements, hardware compatibility, and just because it runs Linux and is easy to program for!

What I envision is a fully contained unit that affixes to the ceiling in the cab of my truck up by the rear-view mirror.  It would:

  • House front and rear-facing cameras.  The RPi has a special connector for a specific camera that works well with it, and there's a cable splitter available to enable connecting more than one camera.  Would use this.
  • The Pi board
  • Sensor accessory board (has accelerometers and stuff)
  • Time/clock accessory board - this enables the RPi to keep track of time even when it's powered off, which is apparently an issue since it doesn't have a battery built in. 
  • Bluetooth and 802.11 b/g/n dongles.  It might be reasonable to even use an external monopole antenna mounted atop the truck for better reception. 
  • A notebook HDD
  • USB GPS dongle
  • A backup battery
I'd have to write some software for this one... I'm unsure if I could throw it together in bash or if it would be complicated enough that I'd want to do it in python.  Software Features would include:
  • Event Awareness:
    • Automatic detection of car starting to trigger logging. 
    • Detection of poweroff to end logging
    • Sudden stops trigger additional logging? 
  • Logging while vehicle is on:
    • Front and rear video
    • GPS data, as available, but expectedly including position and velocity. 
    • Accelerometer data
    • Log wifi access points observed, signal strength, etc (wardriving)
  • Network Services:
    • Seek out and connect to open wifi networks 
    • Auto-connect to home network and automatically sync logged data over to home server. 
    • Tether from phone for internet - look at usb devices connected and auto-start the tether software when phone connects... could even adb issue command to the phone to start the tether software!
    • Share available network via LAN to other devices in the truck...  For example, if I ever get around to building a Nexus tablet CD Deck replacement, it would provide a network connection to it when available.   

References - there are lots of these builds online:

SDR Radio Server

This is a pretty simple one.  Just install linux to the Pi, install the SDR drivers and software, and configure it for the network.  SDR servers allow clients to connect and control the frequency that the SDR radio listens on and, via the network, listen to the radio.

The SDR receivers a lot of people use are cheap, like $20, and work on all kinds of bands, from HF and shortwave, up through the FM stations, VHF, UHF, and beyond.    They are limited by their inability to filter signals received from the antenna, so powerful FM broadcasts can pollute the rest of the spectrum without filters in front of the receiver.  Of course, having a quality antenna is really important as well.

Ideally, I'd have a random wire antenna set up somewhere on my property, running into a window or something, and the RPi would serve the radio over the local network so i could listen from anywhere at home, w/o a tether.  It'd make it easy to listen to SW broadcasts.

Sunday, July 19, 2015

Property Invesetment - Finding ROI

So I've been looking at buying a duplex or something and am trying to understand what is actually a good investment.  I put together a spreadsheet, here, that allows values to be plugged in and it will show the annual increase in value and %return on total investment in the property.

Plug in values in yellow and look at cells in green on the right for return.  Red shows my cost each month toward the mortgage.

It includes mortgage insurance automatically for down payments of less than %20 of the total value, and then stops them once the M.I. cutoff has been reached, configurable in yellow.  I'm not sure if I'm dong this right, but it looks good to me :p

Friday, July 10, 2015

Outlook 2011 Mac OSX Problems

Just some hints for others incase them run into similar issues.  I went on vacation last month and when I returned, Outlook would crash constantly.  Local IT support recommended that I rebuild my profile and, second, try removing my Exchange account and rebuilding the profile again.

This didn't do anything, and somewhere along the way, all of my local folders, the ones that show up under "on my computer", disappeared.  I was still seeing crashes and I had time machine backups, so I charged forward anyway.  I've heard reports of problems resulting from the 14.5.0 update.

What fixed the crashing for me was to completely reinstall Office 2011 (including Outlook).  Google around for the Office Uninstall Tool.  Microsoft provides one.  Reinstall worked fine, although the Update tool had a hard time and I had to grab updates from the Microsoft site to get Office and the Update Tool up to a recent version.

I was hoping I'd be able to try and use an earlier Outlook release, in case one of the updates that my system grabbed when I first got back from vacation had caused my issues, but it complained that my Profile was only compatible with current outlook releases, so I went ahead and updated to the most recent 14.5.2.

My "On my computer" folders were still missing!!!  I restored my profile from a few days ago using a time machine backup, and still nothing.  I started digging through settings to see if I could find a way to load them manually, and something happened that fixed it; it was one of two things:

  • I tried to do an export of all of my contacts, calendar, mail, to a .olm file, just in case, but ended up canceling it because it was too slow (I was trying to write to an SD card where I dump general data).  
  • It's possible that I accidentally clicked the check box in the Preferences -> General -> Folder list -> [ ] Hide On My Computer folders.  By this time I noticed this, I had been through settings once... this may be all that I needed to make these folders show in the first place, but who knows.  If I check it now, they disappear!  
There wasn't much good info coming up in Google about my problem with the local mail, so hopefully this helps someone!