Skip to main content

Ways Django Can Import Things

How many ways can django import a module?

Grep is hard for this.

In .py files

"import (.*)\..*"
"from (.*)\..* import .*"
"patterns\(['"](.*)['"]"
"url(r?['"].*, ['"](.*)"


In INSTALLED_APPS and other settings.

Am I missing any? Better question: Why do I have to wonder if I'm missing any?

Comments

Doug Napoleone said…
You forgot about the magic __path__ hack done to the templatetags 'package' directory. It turns out that app.templatetags.app and django.templtatetags.app are two DIFFERENT imports of the same code and are independent modules with their own globals and locals...

Think about that for a while...
James Bennett said…
You did actually miss one: django.utils.importlib, which is simply a copy of the available-in-future-Python importlib module that Brett Cannon helpfully backported for us to handle all the things in Django (think pluggable backend modules) which require dynamic imports. Previously we used Python's raw __import__ for that, and importlib makes it ever so much simpler, and generally they have to in order to support the sort of dynamic-but-still-concise stuff people like to do in Python.

Anyway, two of the things you've listed are just standard Python import statements, and the other two are just URL-pattern functions which -- if it bugs you that much -- will happily accept the actual callable (or an iterable of patterns, in the case of include()) instead of strings. The string option is mostly just a convenience.

So I'm not sure I really understand the "why do I have to wonder if I'm missing any"; lots of frameworks/libraries have ways to specify something as a string and get it dynamically imported later through some mechanism other than a direct "import whatever" statement.

Oh, and for Doug: the __path__ hacking for templatetags is finally gone in trunk, which means it won't be in 1.2. The last bit of "magic" from magic-removal is finally out, hallelujah.
Unknown said…
Not sure if it is what you were intent on capturing, but there is the import of the Django settings file as a special sort of case. I recently posted some stuff about that at http://blog.dscpl.com.au/2010/03/improved-wsgi-script-for-use-with.html.
James Thiele said…
__import__( ... )
Robert said…
Wouldn't it be nice to standardize these 'import later module strings'* that various python frameworks have as some sort of generic-ized deferredimport('some.python.path.etc') object?

*: which are sometimes necessary due to definition order and cyclic dependencies etc.

Popular posts from this blog

CARDIAC: The Cardboard Computer

I am just so excited about this. CARDIAC. The Cardboard Computer. How cool is that? This piece of history is amazing and better than that: it is extremely accessible. This fantastic design was built in 1969 by David Hagelbarger at Bell Labs to explain what computers were to those who would otherwise have no exposure to them. Miraculously, the CARDIAC (CARDboard Interactive Aid to Computation) was able to actually function as a slow and rudimentary computer.  One of the most fascinating aspects of this gem is that at the time of its publication the scope it was able to demonstrate was actually useful in explaining what a computer was. Could you imagine trying to explain computers today with anything close to the CARDIAC? It had 100 memory locations and only ten instructions. The memory held signed 3-digit numbers (-999 through 999) and instructions could be encoded such that the first digit was the instruction and the second two digits were the address of memory to operate on

The Range of Content on Planet Python

I've gotten a number of requests lately to contribute only Python related material to the Planet Python feeds and to be honest these requests have both surprised and insulted me, but they've continued. I am pretty sure they've come from a very small number of people, but they have become consistent. This is probably because of my current habit of writing about NaNoWriMo every day and those who aren't interested not looking forward to having the rest of the month reading about my novel. Planet Python will be getting a feed of only relevant posts in the future, but I'm going to be honest: I am kind of upset about it. I don't care if anyone thinks it is unreasonable of me to be upset about it, because the truth is Planet Python means something to me. It was probably the first thing I did that I considered "being part of the community" when I submitted my meager RSS feed to be added some seven years ago. My blog and my name on the list of authors at Plan

Pythonic Defined

Introduction Losing is Good Strings Dictionaries Conclusion Introduction Veterans and novices alike of Python will hear the term "pythonic" thrown around, and even a number of the veterans don't know what it means. There are times I do not know what it means, but that doesn't mean I can define a pretty good idea of what "pythonic" really means. Now, it has been defined at times as being whatever the BDFL decides, but we'll pull that out of the picture. I want to talk about what the word means for us today, and how it applied to what we do in the real world. Languages have their strengths and their idioms (ways of doing things), and when you exploit those you embrace the heart of that language. You can often tell when a programmer writing in one language is actually more comfortable with another, because the code they right is telltale of the other language. Java developers are notorious for writing Java in every language they get their hands on. Ho