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?
Labels:

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...
8:26 PM
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.
9:19 PM
Graham Dumpleton 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.
10:01 PM
James Thiele said…
__import__( ... )
1:06 AM
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.
10:11 AM
Post a Comment

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 operat...
1 comment
Read more

Statement Functions

At a small suggestion in #python, I wrote up a simple module that allows the use of many python statements in places requiring statements. This post serves as the announcement and documentation. You can find the release here . The pattern is the statement's keyword appended with a single underscore, so the first, of course, is print_. The example writes 'some+text' to an IOString for a URL query string. This mostly follows what it seems the print function will be in py3k. print_("some", "text", outfile=query_iostring, sep="+", end="") An obvious second choice was to wrap if statements. They take a condition value, and expect a truth value or callback an an optional else value or callback. Values and callbacks are named if_true, cb_true, if_false, and cb_false. if_(raw_input("Continue?")=="Y", cb_true=play_game, cb_false=quit) Of course, often your else might be an error case, so raising an exception could be useful...
1 comment
Read more

How To Teach Software Development

How To Teach Software Development Introduction Developers Quality Control Motivation Execution Businesses Students Schools Education is broken. Education about software development is even more broken. It is a sad observation of the industry from my eyes. I come to see good developers from what should be great educations as survivors, more than anything. Do they get a headstart from their education or do they overcome it? This is the first part in a series on software education. I want to open a discussion here. Please comment if you have thoughts. Blog about it, yourself. Write about how you disagree with me. Write more if you don't. We have a troubled industry. We care enough to do something about it. We hark on the bad developers the way people used to point at freak shows, but we only hurt ourselves but not improving the situation. We have to deal with their bad code. We are the twenty percent and we can't talk to the eighty percent, by definition, so we need to impro...
4 comments
Read more