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Memory efficient Django Queryset Iterator

While checking up on some cronjobs at [YouTellMe](http://www.youtellme.nl/) we had some problems with large cronjobs that took way too much memory. Since Django normally loads all objects into it's memory when iterating over a queryset (even with .iterator, although in that case it's not Django holding it in it's memory, but your database client) I needed a solution that chunks the querysets so they're only keeping a small subset in memory. Example on how to use it: `my_queryset = queryset_iterator(MyItem.objects.all()) for item in my_queryset: item.do_something()` [More info on my blog](http://www.mellowmorning.com/2010/03/03/django-query-set-iterator-for-really-large-querysets/)

  • queryset
  • iterator
  • memory
  • gc
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Email obfuscation filter using ROT13

An email address obfuscation template filter based on the ROT13 Encryption function in Textmate's HTML bundle. The filter should be applied to a string representing an email address. You can optionally pass the filter an argument that will be used as the email link text (otherwise it will simply use the email address itself). Example usage: {{ email_address|obfuscate:"Contact me!" }} or {{ email_address|obfuscate }} Of course, you can also use this on hardcoded email addresses, like this: {{ "[email protected]"|obfuscate }}

  • filter
  • javascript
  • email
  • textmate
  • obfuscation
  • rot13
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Render specific blocks from templates (useful for AJAX, alternative)

Special thanks to the author of snippet 769 who provided most of the code for this snippet. Major differences: 1.Simpler/better handling of "extends" block tag 2.Searches If/Else blocks 3.Less code 4.Allow list of templates to be passed which is closer to the behavior of render_to_response

  • template
  • block
  • templates
  • render
  • context
  • blocks
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Admin Image Widget

A FileField Widget that displays an image instead of a file path if the current file is an image. Could also be used with sorl.thumbnail to generate thumbnail images. **Example** class FileUploadForm(forms.ModelForm): upload = forms.FileField(widget=AdminThumbnailWidget) class Meta: model = FileUpload class FileUploadAdmin(admin.ModelAdmin): form = FileUploadForm admin.site.register(FileUpload, FileUploadAdmin)

  • image
  • newforms-admin
  • widget
  • file
  • nfa
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Generic CSV Export

This will generically add csv exporting to your views in the admin. It will default to exporting the entire table you see (without paging). If the table only has one column, it will export the fields the the model. You can overide this functionality. I ended up creating my own admin/change_list.html to apply this functionality universally: {% extends "admin/base_site.html" %} {% load adminmedia admin_list i18n %} {% block stylesheet %}{% admin_media_prefix %}css/changelists.css{% endblock %} {% block bodyclass %}change-list{% endblock %} {% if not is_popup %}{% block breadcrumbs %}<div class="breadcrumbs"><a href="../../">{% trans "Home" %}</a> &rsaquo; {{ cl.opts.verbose_name_plural|capfirst|escape }}</div>{% endblock %}{% endif %} {% block coltype %}flex{% endblock %} {% block content %} <div id="content-main"> {% block object-tools %} <ul class="object-tools"> <li><a href="csv/{%if request.GET%}?{{request.GET.urlencode}}{%endif%}" class="addlink">Export to CSV</a></li> {% if has_add_permission %} <li><a href="add/{% if is_popup %}?_popup=1{% endif %}" class="addlink">{% blocktrans with cl.opts.verbose_name|escape as name %}Add {{ name }}{% endblocktrans %}</a></li> {% endif %} </ul> {% endblock %} <div class="module{% if cl.has_filters %} filtered{% endif %}" id="changelist"> {% block search %}{% search_form cl %}{% endblock %} {% block date_hierarchy %}{% date_hierarchy cl %}{% endblock %} {% block filters %}{% filters cl %}{% endblock %} {% block result_list %}{% result_list cl %}{% endblock %} {% block pagination %}{% pagination cl %}{% endblock %} </div> </div> {% endblock %}

  • admin
  • export
  • csv
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Fire Eagle example: views.py from wikinear.com

The views.py used by [wikinear.com](http://wikinear.com/) - see [http://simonwillison.net/2008/Mar/22/wikinear/](http://simonwillison.net/2008/Mar/22/wikinear/) For a more comprehensive API wrapper for Fire Eagle, take a look at [fireeagle_api.py](http://github.com/SteveMarshall/fire-eagle-python-binding/tree/master/fireeagle_api.py)

  • location
  • fireeagle
  • oauth
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Custom managers with chainable filters

The Django docs show us how to give models a custom manager. Unfortunately, filter methods defined this way cannot be chained to each other or to standard queryset filters. Try it: class NewsManager(models.Manager): def live(self): return self.filter(state='published') def interesting(self): return self.filter(interesting=True) >>> NewsManager().live().interesting() AttributeError: '_QuerySet' object has no attribute 'interesting' So, instead of adding our new filters to the custom manager, we add them to a custom queryset. But we still want to be able to access them as methods of the manager. We could add stub methods on the manager for each new filter, calling the corresponding method on the queryset - but that would be a blatant DRY violation. A custom `__getattr__` method on the manager takes care of that problem. And now we can do: >>> NewsManager().live().interesting() [<NewsItem: ...>]

  • manager
  • queryset
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ImageURLField for forms

A URL field specifically for images, which can validate details about the filesize, dimensions and format of an image at a given URL, without having to read the entire image into memory. Requires [Python Imaging Library](http://www.pythonware.com/library/pil/). *4th October, 2008* - updated for 1.0 compatibility.

  • image
  • pil
  • validation
  • url
  • form
  • field
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Sort Table Headers

Handles creation of `order_by` criteria based on GET parameters and provides context variables to be used when generating table header sort links which respect the current sort field and direction, reversing the direction when the same header is sorted by again. Sample view: from somewhere import SortHeaders from django.contrib.auth.models import User from django.shortcuts import render_to_response LIST_HEADERS = ( ('Username', 'username'), ('First Name', 'first_name'), ('Last Name', 'last_name'), ('Email', None), ) def user_list(request): sort_headers = SortHeaders(request, LIST_HEADERS) users = User.objects.order_by(sort_headers.get_order_by()) return render_to_response('users/user_list.html', { 'users': users, 'headers': list(sort_headers.headers()), }) Sample template: {% load my_tags %} <table cellspacing="0"> <thead> <tr> {% table_header headers %} </tr> </thead> <tbody> {% for user in users %}<tr class="{% cycle odd,even %}"> <td><a href="{{ user.get_absolute_url|escape }}">{{ user.username|escape }}</a></td> <td>{{ user.first_name|escape }}</td> <td>{{ user.last_name|escape }}</td> <td>{{ user.email|escape }}</td> </tr> {% endfor %} </tbody> </table> Sample inclusion tag: from django import template def table_header(context, headers): return { 'headers': headers, } register = template.Library() register.inclusion_tag('table_header.html', takes_context=True)(table_header) Sample inclusion tag template: {% for header in headers %}<th{{ header.class_attr }}> {% if header.sortable %}<a href="{{ header.url|escape }}">{% endif %} {{ header.text }} {% if header.sortable %}</a>{% endif %} </th>{% endfor %}

  • sort
  • table
  • headers
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Left Outer join Q object

QLeftOuterJoin object allows you to create 'LEFT OUTER JOIN' sql query. It is very usefull if you have to define ForeignKey to 'null=True' (select_related will not work with null=True). You are allowed to use QLeftOuterJoin like Q object. Example: `QLeftOuterJoin('thread_last_post', Post, 'pk', Thread, 'last_post')` It will generates SQL like: LEFT OUTER JOIN appname_post AS thread_last_post ON thread_last_post.id = appname_thread.last_post_id Table could be model or string.

  • sql
  • q
  • query
  • join
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Sanitize HTML filter

Originally posted by [akaihola](http://www.djangosnippets.org/users/akaihola/) as [snippet #169](http://www.djangosnippets.org/snippets/169/). I just redid it as a filter.

  • html
  • sanitize
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Choice Field and Select Widget With Optional Optgroups

Renders an select field with some optgroups. Some options can be outside the optgroup(s). The options and labels should be in a tuple with ((label, choices),) where choices is a tuple ((key, value), (key2, value2)). If a label is null or blank, the options will not belong to an opt group.

  • newforms
  • widgets
  • select
  • optgroup
  • option
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TestCase helpers

I use these helper methods in my unit tests. They turn many simple getting-and-posting tests into one-liners. Definitely a work in progress, and I can't be the only person who has done this sort of thing -- comments are more than welcome.

  • testing
  • tests
  • unittest
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Author: pbx
  • 10
  • 11

Cache Any Function

A decorator similar to `cache_page`, which will cache any function for any amount of time using the Django cache API. I use this to cache API calls to remote services like Flickr in my view, to prevent having to hit their servers on every request. I posted a sample function which uses the [delicious API](http://www.djangosnippets.org/snippets/110/) in the function, also. **Update**: It now also will put in a temporary 'in-process' variable (an instance of `MethodNotFinishedError`) in the cache while the function is processing. This will prevent the cache from calling the method again if it's still processing. This does not affect anything **unless you're using threads**.

  • cache
  • function
  • threading
  • threads
  • thread
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