Amble Ramble

Django Setup from Shell

Roy — Thu, 01 Sep 2011 21:50:37 +0000

Django uses a number of settings typically defined in the settings module within a project. These can be loaded into the interactive python shell for extra interactive fun.

from django.core.management import setup_environ from myapp import settings setup_environ(settings)

Generating PNGs from matplotlib on a Server

Roy — Thu, 24 Mar 2011 23:38:05 +0000

Migrated from my local machine to a remote server a data analysis that plots data using Python’s matplotlib and saves the plots to PNGs. Running the analysis turned up an unexpected error that ends by noting:

no display name and no $DISPLAY environment variable

Bummer. A quick search turned up more documentation on this from both the official matplotlib documentation on using matplotlib in a webapp and generating PNGs in matplotlib when DISPLAY is not defined.

The two typical solutions are to explicitly set a backend in the Python code (this must be done before any other matplotlib imports):

import matplotlib # Force matplotlib to not use any Xwindows backend. matplotlib.use('Agg')

or set the backend using the matplotlibrc file.

Summing a Column of Numbers

Roy — Mon, 07 Feb 2011 06:09:55 +0000

I’m a command line junkie who only turns to higher level scripting when
a line of piped together commands falls short. A common task that I run
into is summing a column of data from a text file. Typically, my data
is in a gnuplot friendly format makes extracting the column easy:

grep -v "^#" bandwidth.dat | cut -f3 -d' '

Now what is an easy way to sum that data? I’ve seen solutions using
awk, but I’m not much of an awk fan. Much more exciting is a version
using paste:

grep -v "^#" bandwidth.dat | cut -f3 -d' ' | paste -sd + | bc