Metaprogramming and other topics
python-from-c++ Calling Python from C++ Have you ever been writing C++ and you find yourself writing non-performance-critical code that would be absolutely trivial in Python? Or perhaps there is some complex problem that has an optimized solution in a python package, and if you could just call it from your C++ code life would be…
When I’m making a python package, I usually write an __init__.py which lifts the packages modules into the package namespace. Assume you have a package like this: my_package/ __init__.py module1.py module2.py module3.py If you leave the __init__.py blank, you cannot do: import my_package my_package.module1 This will result in an error that looks like: ————————————————————————— AttributeError…
Ray Tracing A Ray Tracing Adventure I’ve been entertaining the idea of writing a ray tracer for a while now and last weekend I stumbled across the excellent book “Ray Tracing in One Weekend” by Peter Shirley. I really enjoyed the read and had even more fun following along and implementing it. I dismissed Peter’s…
Inter-process communication Interprocess communication in Python with shared memory The python ecosystem has rich support for interprocess communication (IPC). The multiprocessing API allows multiple python processes to coordinate by passing pickled objects back and forth. Python has full support for signal handling, socket IO, and the select API (to name just a few). In this…
In most programming languages, you can segfault your program by going too deep in a recursive function. In CPython (the reference implementation that you are probably using), recursion is limited to a fixed number of consecutive recursive calls. The default maximum recursion can be checked by calling sys.getrecursionlimit(). On my machine, this returns 1000 for…
In my last post, I introduced Cython as a tool to speed up your python code by generating a native module. That’s great if you have your solution already prototyped in pure python, but sometimes you may want to take advantage of a pre-existing library that solves your problem. If that library is written in…
Todays post is all about one of the tools to speed up your Python code. Cython can be installed with pip: pip install cython What the heck is Cython anyway? From one point of view, Cython is a language that is very close to a superset of Python syntax. That is to say, most Python…
Today I’m going to talk about python metaclasses. Metaclasses are generally considered to be an advanced python topic, but I promise that it’s really not that bad. The first step on the path to understanding metaclasses is to recognize that in python, even though you don’t need to specify types (as you do in many…
Let’s talk about the yield keyword in python. yield? So what is yield all about? Let’s fire up an IPython Read-Evaluate-Print-Loop (REPL) and dive right in with an example: In [1]: def yielder(): …: i = 5 …: while i > 0: …: yield i …: i -= 1 So what happens when we call…
This post is a bit of a departure from my normal Python evangelism. Instead, I’m going back to my C roots and exploring the somewhat mystical world of the LD_PRELOAD environment variable. TL;DR: LD_PELOAD is a (linux) variable you can set to hijack the symbol resolution order for linked libraries. First lets consider a basic…