Three good StackOverflow answers on Python topics
Here are three thorough answers on Python topics from StackOverflow. Metaclasses Yield, iterables, iterators, generators Decorators
Apache Cassandra presentation slides
Apache Cassandra is a column-store with a p2p distribution architecture. Yesterday I did a presentation about Cassandra at Grontmij, Glostrup, Denmark. I made the slides in Google Docs, and they’re public: slides.
Creating visually random images
How complicated does a mathematical function, pseudorandom(x), have to be to create something that seems random, and how do you check whether it seems random? Looking at a long list of numbers is not a good way, because our ability…
How to remove extended attributes from a file edited with TextMate
If you run ‘ll -l’ sometimes a file has ‘@’ permission. This means that the file has extended attributes. TextMate may extended attributes to a file. Consider a fictional Python file called xxx.py edited with TextMate: View extended attributes: $…
Incrementing part of an array in numpy
given a (2D) array a, and a smaller (2D) array b, how can you add the smaller array to the bigger array at some offset in numpy? >>> a = zeros((4,4), dtype=int) >>> a array([[0, 0, 0, 0], [0, 0,…
Hello world of raster creation with GDAL and Python
Mostly so I myself can remember how to do it, here is how to create a random geotiff with GDAL in Python Note: the width and height are given in opposite order in the GDAL raster and numpy arrays! import…
Using Cython, psyco and other tricks to make Python run faster
This is a good post showing how “perrygeo” uses Cython to speed up a pure Python function. The comments also discuss alternatives and options: Using psyco instead of Cython Using optimization flags for gcc Using xxx instead of math.xxx
Quick benchmarking of Python code with timeit
How long does [insert code snippet] take in Python? Find out with the timeit module, in Python since 2.3. Below I time how long it takes to make a list with a 1000 zeros, [0,0,0,…], using different Python code snippets.…
Transforming geographical and projected coordinates in Python
pyproj is a Python interface to the PROJ.4 () functions. It allows you to transform coordinates between coordinate systems. Install pyproj using pip Assuming you’re using pip to install Python packages: $ pip install pyproj
Why Tor is slow
I tried the Tor browser today, and was amazed at how slow it was. As Tor’s user base has grown, the performance of the Tor network has suffered. This document describes the current understanding of why Tor is slow, and…