I looove chai and I'm always looking for something that satisfies my cravings. So far I have only once tried hand-making my own chai spice mix, and it didn't turn out that well... I'll let you know if I ever come up with something good! Meanwhile I am trying lots …

Writing better tests is a lifelong pursuit, apparently.

One thing I've been noticing lately, especially while doing code reviews, is that we are usually thinking about how do I know the code worked.

Great! But we are usually not thinking ahead about what am I going to do when the …

If you want to keep your customers happy, one foundation that your product process needs is a shared understanding across your entire organization around at what stage of development can you commit to a release date.

When sales is involved, this also translates to: at what point can the sales …

Here's a quick hack to help when you're lost in a too-large Python inheritance tree. What class provides the most specific implementation of a method or attribute?

def find(cls, name):
    for sup in cls.mro():
        if name in sup.__dict__:
            return sup.__name__
    return None

def find_all_vars(cls):
    for …

Thread locals are an interesting idea: a way to give each thread its own storage, useful for global state that you don't want to share between threads.

The obvious caveat is that threadlocals are still effectively global (for the current thread), and like all global state, should be treated with …

People sometimes ask me for career advice in software startups. For a long time I didn't know what to say. When I finally noticed a pattern in my career, it was like a blinding light.

Now I know the single most important thing to advise:

Make sure the logo is …

TL;DR When scheduling features for a quarter, it's very risky to plan on delivering multiple projects that are starting from scratch.

Let's call this the "Shiny New Quarter" approach to planning.

Is this self-evidently problematic? Maybe to you. But apparently not to everyone, because I've seen it done repeatedly …

I had cataract removal surgery this year. Twice: My left eye was done in May 2016, and my right eye in October.

Since most people I know have no experience of this and are curious about it, I wrote up a description of the experience as a Q&A.

Aren't …

It seems clean and safe 99% of the time.

And then you have that one accident...

As a birthday present to myself, and a fit of fiddling while Rome burns, I have junked the ooooooold website, thrown out a bunch of cruft, and finally started that blog I never got around to.

Most of it is geeky programming stuff, but with forays into music and other …

(Drafted 2016-06-22; finished 2016-11-23)

Shortly after Prince died, one of my favorite podcasts, "Switched On Pop", paid tribute to Prince by talking about one of his best-known and most distinctive singles, "When Doves Cry".

Weirdly, while this is a podcast that loves to talk about the parallels between music and …

In the spirit of "Falsehoods Programmers Believe" (my favorite is probably "Falsehoods Programmers Believe About Time"), I offer this, about working with third-party REST APIs.

"Believe" is a bit of a strong word here. Beliefs are deep things that are resistant to change. These are more like assumptions or wishes …

Does this return all the data?

urllib2.urlopen(url).read()

The answer appears to be "not always".

http://stackoverflow.com/questions/7174927/when-does-socket-recvrecv-size-return https://github.com/CVL-dev/feedparser/issues/1

I can't seem to get a definitive answer here, nor a reproducible demonstration of it failing.

Does anybody know for …

In Python we often use the mock library to do dependency injection for tests. Recently I came across a really confounding edge case that can be easily avoided if you know about it.

Mock intro redux

(Skip this section if you're already familiar with mock.)

Let's say we have a …

Some notes on my emacs setup. Maybe this should go in README for my dotemacs.

Python

Which mode?

There is python-mode.el, and python.el. I have settled on python-mode from the elpa repositories.

Rope?

I tried ropemacs, and really like it when it works. For simple refactorings it can …

So it turns out there are some painful edges if you start trying to do SQLAlchemy declarative ORM classes in an existing Django app. (For example, if you're gradually replacing the Django ORM in your code with Sqlalchemy ORM). It boils down to:

• The django testrunner (or django-nose) changes the …

TL;DR graphite graphs look wrong when viewing a time period larger than a few hours. hitcount is the cure.

It turns out counters are bucketed as hits per time slice, not as permanently incrementing numbers.
http://code.hootsuite.com/accurate-counting-with-graphite-and-statsd/ helps a lot to explain how this works. For …

Here's a typical loop that checks for some condition and breaks the first time it passes:

    def list_contains_urls(maybe_urls):
        for url in maybe_urls:
             if url.startswith('http'):
                  return True
        return False

Can we do that more concisely? Sure.

    def list_contains_urls(maybe_urls):
         return any(u for u in maybe_urls if u …

How to create a brand new git repository from an existing hg repository. This is not explained on http://hg-git.github.com/

  easy_install hg-git
  # Now edit your ~/.hgrc as per http://hg-git.github.com/

  # Now make a bare git repository. Yes, bare.
  git init --bare ~/my-git-repo    # the --bare is important …

For various reasons that might be explained in more retroblogging, around January 2014 I got fed up with OSX and decided to switch back to Linux. I got things more or less working on my Macbook Air. (Later, in 2016, replaced with a Macbook Pro.)

TL;DR: It's okay, and …

Django's settings.py is evil.

Why? Because in terms of security, it is a bomb waiting to go off. Typically your database settings go in there, and potentially other sensitive stuff (salts, service API keys, what have you).

By encouraging you to put a settings.py file in your project's …

Consider:

>>> ''.split()
[]

That seems okay... split an empty string on whitespace and you get an empty list, sure, why not.

Except that in every other case, if you split a string on a separator that it doesn't contain, you get a list containing the original string - even if the original …

(Updated 2018 with a more modern Python 3 tip)

I always forget how to write a class that can be used as both a decorator and a context manager. It's a handy trick, but I don't do it often enough to remember, so, here it is.

In Python 2, you …

What's the difference between these?

>>> zipped = zip(iter1, iter2)
>>> mapped = map(None, iter1, iter2)

The answer turns out to be depend on whether iter1 and iter2 are the same length. Pretty subtle: zipped is truncated to the length of the shortest of (iter1, iter2). mapped is the same length as …

A coworker (hi Will) just introduced me to pdbpp.

As a longtime pdb user, I must say this is SOOO GOOD. Two features alone are worth it: syntax highlighting, and the ll command which prints the entire function around the current line.

One wrinkle is that at work we still …

A couple of coworkers (Sean O'Connor, Dan Frank) bailed me out of a sticky git scenario. I'd been working on a branch for way too long and somebody else made wildly incompatible changes to a couple of the more important files I'd changed. When this happens, I'm prepared to accept …

Somebody at work recently asked if it were possible in Bash to have stdout and stderr both visible on the terminal but also copied to separate log files.

Normally when I think of console output and file logging at the same time, I think of "tee". But it can only …

Debugging with print statements is kind of like the old 2D Mario games. You get a little bit forward, learn a little more about the world you're exploring until something sends you back to the beginning. You get a little bit farther each time, but you keep having to go …

Django as it is in the wild is not a web software framework. It is a web site framework.

(disclaimer re. complaining: http://commandcenter.blogspot.com/2011/12/esmereldas-imagination.html )

What does this mean and why?

For some things, I love Django. It hits a particular sweet spot really well …

A little tip for working with the mock library. Let's say you need to set up some child attributes, like for example you're mocking up a django.contrib.auth.User, and you want it to be a logged in user:

>>> user = mock.Mock()
>>> user.username = 'Bob'
>>> user.is_authenticated.return_value = True …

I love the combination of virtualenv and pip requirements files. This is a great 95% solution to the problem of deploying and distributing known-good sets of python packages, safely (semi-)isolated from other python environments on the same system.

The --no-site-packages option is great because it makes your installation isolated …

The venerable Cron in its various forms (vixie-cron, anacron, etc) is good at what it does, but there are a lot of things that could make it much better to work with. For example:

• "Debug" mode: run all the rules in a given crontab file right now and put errors …

Want to merge two dictionaries into a new third dictionary without modifying either of the originals? Easy:

>>> dict3 = dict(dict1, **dict2)

Keys in dict2 would override matching keys in dict1. And, as usual, mutable values would be preserved by reference...

Personally I've always wished that dicts would define __add__ to …

I haven't automated this yet, but will if I ever do this again.

• Get a trac wiki export: trac-admin $PWD wiki dump /tmp/wiki-dump/

• cd /tmp/wiki-dump

• Rename the home page: mv WikiStart Home

• Clean up trac-specific junk: rm -f Wiki* Trac* CamelCase BadIP PageTemplates Inter* SandBox TitleIndex RecentChanges

• Trac …

Django can be run under any WSGI server, which means you can use it in a WSGI pipeline. Deploying Django under mod_wsgi is well documented, but sometimes you want to test your WSGI pipeline on a local server without mucking with configuring nginx or apache, and/or try out some …

If you want your users to report bugs, don't put hurdles in their way.

Today I was trying to convert a word processing document to plain text and make it look reasonably nice. I started with OpenOffice's "save as plain text" feature, but it wasn't handling tables very well.

So …