The Installation

Please join me this month as we dive head first into building things with Python (and Django) emphasizing location information.

I hope at the end of this you’re up to speed on building basic location-aware web apps and no longer scared that you suck too much at math to do this kind of stuff. It’s not scary or hard, I promise.

I’m going to be focusing on Python most of the time, and the Django framework some of the time. For a database I’ll be using PostGIS because it’s what I use in production, and I’ve never taken the time to install and configure spatiality. Don’t even ask about MySQL, its spatial support sucks.

Unlike Django itself, which is very easy on prereqs, GeoDjango needs a bunch of support before it works properly. This scares people off, but you shouldn’t be afraid – it’s very easy to get over this speed bump.

I personally use Homebrew on my Macs and a list of apt-get-able stuff on Linux. The Django Docs talk about installation quite extensively, in https://docs.djangoproject.com/en/1.3/ref/contrib/gis/install/#ref-gis-install and https://docs.djangoproject.com/en/1.3/ref/contrib/gis/tutorial/#introduction but I’m adding my “quickstarts” below.

Mac:

  • brew install git
  • brew install bazaar exiftool gdal geos imagemagick libtiff readline redis
  • brew install postgresql postgis
  • sudo easy_install pip
  • sudo pip install virtualenv virtualenvwrapper

Linux: (this is for Ubuntu 11.10, and this is more than you need bare minimum. It’s just what I install by default to get a server ready for me.)

  • apt-get install libgeos-3.2.2 proj postgis gdal-bin postgresql-9.1-postgis postgresql-9.1 libgdal1-dev subversion make python-httplib2 python-lxml python-setuptools python-yaml apache2 apache2.2-common apache2-mpm-worker apache2-threaded-dev apache2-utils libexpat1 ssl-cert libapache2-mod-rpaf python-dev python-imaging python-docutils python-markdown python-dateutil flex bzr gettext screen imagemagick mercurial python-simplejson g++ libperl-dev unzip sl locate git
  • easy_install pip
  • pip install virtualenv virtualenvwrapper

One hangup I ran into with this install tactic on 11.10 is that in Postgres 9.1 the Postgres setting “standard_conforming_strings” is now on by default. This causes an issue with the WKB (well-known binary, a format used for geospatial information) and must be turned off. You’ll find it near the bottom of /etc/postgresql/9.1/main/postgresql.conf

Everything I’ll be doing will be in clean virtualenvs. If you’re not familiar with them, they are definitely worth a read. Essentially, no more Python path issues. It sequesters all of your code for a given project off on its own. I recommend you use virtualenvwrapper as well, it makes working with them much easier. The only tricky part is making sure `source /usr/local/bin/virtualenvwrapper.sh` gets placed in your .bashrc or .bash_profile. You also need to restart your shell to pick up the changes.

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