Metaprogramming and other topics
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…
When I was starting out with Python I introduced a bug into my code because I didn’t understand how scoping works in closures. This is a pretty common pitfall, so here is a post exploring the mistake and how to avoid it. Check out this code: import threading def threaded_print(): for i in range(10): def…
Memoization (a key concept in dynamic programming) is a fancy word that basically means storing the results of computation and never recomputing. Instead, you simply look up the already computed value. Any pure function can be memoized. Memoization can have a dramatic affect on the runtime of algorithms which use the results of computation multiple…
In Python, methods or attributes that begin with _ are considered ‘private’. There isn’t public/private/protected levels of access as there are in some other languages, but a single _ is an indication that the method or attribute is not part of the public API. There is further meaning for things that start with two of…
I’ve had the pleasure of talking to several folks who are involved in cybersecurity in one form or another. It’s surprising to me how few of us have actually gone through the trouble of crafting an exploit by hand. I think that the process of identifying a vulnerability and exploiting it by hand leads to…