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All snippets written in Python

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compressing polygons for geodjango

The code shown allows you, in GeoDjango, to reduce the number of points in your polygons. It helps reduce storage needs and makes queries run faster, at the cost of some precision. It provides a variation on the simplify() method that comes with the GEOS API, allowing you to specify a number of points instead of a distance tolerance. It is set up as a management command so that you can run it with python manage.py. See the django docs for how to set that up. The example shown assumes a table called CountyBorders with fields "name" and "mpoly." It should be straightforward to adapt it for your needs. Look at the first three lines of the simplify() method in particular for customization. The rest of the code is pretty generic, and it should run fast enough in a one-time batch process for most needs. The algorithm tries to keep the 75 points that provide the most definition for the shape. Each point in a polygon defines a triangle with its immediate neighbors. If that triangle has no area (the degenerate case), it is a midpoint on the segment between its neighbors and adds no value whatsoever. This principle is extended to say that the larger the triangle, the more value the point has in defining the shape. (You can find more refined algorithms, but this code seems to work fine by visual inspection.)

  • geodjango
  • polygons
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Filtering foreignkey fields in django admin

Sometimes you need to filter foreignkey choices in admin interface, to objects created by user or meeting some other condition. In django 1.0 there is no formfield_for_foreignkey method in ModelAdmin class so we have to make a workaround. Here is the solution I have found to be the easiest for me.

  • filter
  • admin
  • foreignkey
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Python fixup handler for Apache

If you have another application in the same Apache virtual host and also want to use the authentication from Django - this might help. It uses the Django cookie - so it will not work in another Apache virtual host.

  • authentication
  • apache
  • fixup-handler
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Django app WSGI

If you want to have your wsgi as general as possible (for eg. different environments) without any hardcoded paths, this example might help you...

  • wsgi
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Load local settings

If you have a production, staging, testing and development environment, you might want to have a global checked in (in your version control system) settings.py for production + a local settings.py to override various settings (like database connection). It's also good for development, since developers don't - by incident - commit to the production settings.py, since they can use their local settings, that should be ignored (.cvsignore, .svnignore or similar).

  • settings
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CodeLookupField

This is a custom form-field designed to make those optional "enter a discount code" fields a little easier to deal with. You create one like this: code = CodeLookupField(model=MyModel, field_name='slug', max_length=20) And then when you validate your form, cleaned_data['code'] will be the actual object if anything was retrieved, or None if the user entered a bad piece of data.

  • forms
  • field
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LoginAsForm - Login as any User without a password

Sometimes the only way to reproduce a bug on a production site is to login as the User who encountered it. This form allows you to login as any user on the site. **Usage** @staff_member_required def login_as(request, template="login_as.html"): data = request.POST or None form = LoginAsForm(data, request=request) if form.is_valid() form.save() return HttpResponseRedirect(settings.LOGIN_REDIRECT_URL) ...

  • forms
  • login
  • auth
  • authenticate
  • form
  • auth.contrib
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Custom nose runner

This method is replacement for django test runner. It uses nose test runner, which will discover all tests in the application (not even in tests module of applications). For installing put in settings.py: `TEST_RUNNER = 'nose_runner.run_tests'` where *nose_runner* is module containing the code

  • test
  • nose
  • testrunner
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Template context debugger with (I)Pdb

This allows you to set up a breakpoint anywhere in your template code, by simply writing {% pdb_debug %}. You can then access your context variables using context.get(..) at the pdb prompt. Optionally, install the ipdb package for colors, completion, and more (easy_install ipdb).

  • template
  • debug
  • context
  • pdb
  • ipdb
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Captcha without Freetype or the Python Imaging Library (PIL)

If, like me, you've had trouble installing the [Python Imaging Library](http://www.pythonware.com/products/pil/) or [FreeType](http://freetype.sourceforge.org), you may have also had trouble getting a captcha to work. Here's my quick and dirty workaround — be warned, this is _very_ low level security, and shouldn't be used on high-profile sites. Originally published at <http://gregbrown.co.nz/code/django-captcha-without-freetype-or-pil/> Credit to the author of [django-simple-captcha](http://code.google.com/p/django-simple-captcha/), from whom I borrowed most of this code. ### Usage from django import forms from ABOVE-FILE import CaptchaField class CaptchaTestForm(forms.Form): myfield = forms.TextField() security_check = CaptchaField()

  • captcha
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EditingMiddleware (quickly open views and templates in your text editor!)

Heavily based on [Snippet 1033](http://www.djangosnippets.org/snippets/1033/) and [Snippet 766](http://www.djangosnippets.org/snippets/766/). This snippet tracks what view and templates are used to render HTML responses and inserts a small dialog in the top right corner of the output with links to all the files. If your text editor support opening files from a browser protocol you can click the links to open the files right up! For example TextMate supports the `txmt://` protocol. Really saves some time if you find yourself editing a lot of templates. ![txt](http://img.skitch.com/20090602-11df2tfg273p99i95nfx6a74qe.png) **Usage** 1. Save this snippet in a file called `middleware.py` on your Python Path. 2. Add `middleware.EditingMiddleware` to your `MIDDLEWARE_CLASSES`. 3. Browse to any HTML page on your site!

  • middleware
  • editing
  • texteditor
  • editor
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Sometimes Tag

Adds a templatetag that works like an if block, but . The one and only argument is a float that reflects the percentage chance. It defaults to .2, %20. {% sometimes %} <img src='spy_behind_sniper.jpg'/> {% else %} <img src='sniper.jpg'/> {% endsometimes %} -- or -- {% sometimes .001 %} You win! {% else %} Sorry, not a winner. Play again! {% endsometimes %} -- or -- {% sometimes .5 %} This shows up half the time. {% endsometimes %}

  • tag
  • random
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