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Building GIS Web Apps with Python & Django ! Brad Montgomery MEMpy: Memphis Python User Group (mempy.org) Tennessee Data Commons (tndata.org)

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The Web framework for perfectionists with deadlines. ! http://djangoproject.com

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MVC-inspired

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MTV (model, template, view)

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Batteries Included • An object-relational mapper (ORM) • Form Validation • Testing Tools • Migrations (recently added to Django) • Built-in apps (admin, auth, caching, sessions, sitemaps, syndication, gis, … more)

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Community • 100’s of 3rd-party, open source apps • Many are MIT or BSD Licensed. • djangopackages.com

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Let’s Build a Blog!

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Directory Structure sampleproject/! !"" blog! # !"" __init__.py! # !"" admin.py! # !"" migrations! # # $"" __init__.py! # !"" models.py! # !"" tests.py! # $"" views.py! # !"" templates/

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Projects & Apps sampleproject/! !"" blog! # !"" __init__.py! # !"" admin.py! # !"" migrations! # # $"" __init__.py! # !"" models.py! # !"" tests.py! # $"" views.py! # !"" templates/ Most of your work is here.

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models.py from django.contrib.auth.models import User! from django.contrib.gis.db import models! ! ! class Post(models.Model):! author = models.ForeignKey(User)! title = models.CharField(max_length=128)! content = models.TextField()! slug = models.SlugField(max_length=128, unique=True)! published_on = models.DateTimeField(auto_now_add=True)! published_at = models.PointField(srid=4326)! ! objects = models.GeoManager()

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models.py from django.contrib.auth.models import User! from django.contrib.gis.db import models! ! ! class Post(models.Model):! author = models.ForeignKey(User)! title = models.CharField(max_length=128)! content = models.TextField()! slug = models.SlugField(max_length=128, unique=True)! published_on = models.DateTimeField(auto_now_add=True)! published_at = models.PointField(srid=4326)! ! objects = models.GeoManager() corresponds to a database table

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models.py from django.contrib.auth.models import User! from django.contrib.gis.db import models! ! ! class Post(models.Model):! author = models.ForeignKey(User)! title = models.CharField(max_length=128)! content = models.TextField()! slug = models.SlugField(max_length=128, unique=True)! published_on = models.DateTimeField(auto_now_add=True)! published_at = models.PointField(srid=4326)! ! objects = models.GeoManager() columns in the table

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models.py from django.contrib.auth.models import User! from django.contrib.gis.db import models! ! ! class Post(models.Model):! author = models.ForeignKey(User)! title = models.CharField(max_length=128)! content = models.TextField()! slug = models.SlugField(max_length=128, unique=True)! published_on = models.DateTimeField(auto_now_add=True)! published_at = models.PointField(srid=4326)! ! objects = models.GeoManager()

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models.py from django.contrib.auth.models import User! from django.contrib.gis.db import models! ! ! class Post(models.Model):! author = models.ForeignKey(User)! title = models.CharField(max_length=128)! content = models.TextField()! slug = models.SlugField(max_length=128, unique=True)! published_on = models.DateTimeField(auto_now_add=True)! published_at = models.PointField(srid=4326)! ! objects = models.GeoManager()

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gis fields from django.contrib.gis.db import models! ! class SomeModel(models.Model):! line = models.LineStringField()! poly = models.PolygonField()! geometry = models.GeometryField()! ! lines = models.MultiLineStringField()! points = models.MultiPointField()! polygons = models.MultiPolygonField()! geometries = models.GeometryCollectionField()! ! objects = models.GeoManager()

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ORM/gis lookups # Get a list of all Post objects! Post.objects.all()

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ORM/gis lookups # Get Posts mentioning “Foo”! Post.objects.filter(content__contains=“Foo”)

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ORM/gis lookups # Get Posts mentioning “Foo”! Post.objects.filter(content__contains=“Foo”) A field on our model

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ORM/gis lookups # Get Posts mentioning “Foo”! Post.objects.filter(content__contains=“Foo”) 2 underscores! “dunder”

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ORM/gis lookups # Get Posts mentioning “Foo”! Post.objects.filter(content__contains=“Foo”) A lookup operation

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ORM/gis lookups # Get Posts mentioning “Foo”! Post.objects.filter(content__contains=“Foo”) The value we want to find.

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ORM/gis lookups # Get a single Post object! Post.objects.get(id=7)

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ORM/gis lookups ! # Get the city using a WKT! City.objects.get(! ! mpoly__contains=‘POINT(-95.3385 29.7245)’! )!

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ORM/gis lookups ! # Get the city where a Post was published! City.objects.get(! ! mpoly__contains=post.published_at! )!

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ORM/gis lookups from django.contrib.gis.measure import D! ! # Find other posts published within 5 Miles.! radius = (post.published_at, D(mi=5))! Post.objects.filter(! published_at__distance__lte=radius! )

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ORM/gis lookups Distance Lookups ! •distance_lt •distance_lte •distance_gt •distance_gte •dwithin Spatial Lookups ‣bbcontains ‣bboverlaps ‣covers ‣crosses ‣overlaps ‣intersects ‣touches ‣within ‣…more!

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views.py from django.shortcuts import render_to_response! from django.template import RequestContext! from models import Post! ! def display_post(request, post_slug): ! post = Post.objects.get(slug=post_slug)! template_data = {'post': post}! template = "blog/post.html"! ! return render_to_response(! template,! template_data,! context_instance=RequestContext(request)! )

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views.py from django.shortcuts import render_to_response! from django.template import RequestContext! from models import Post! ! def display_post(request, post_slug): ! post = Post.objects.get(slug=post_slug)! template_data = {'post': post}! template = "blog/post.html"! ! return render_to_response(! template,! template_data,! context_instance=RequestContext(request)! )

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views.py from django.shortcuts import render_to_response! from django.template import RequestContext! from models import Post! ! def display_post(request, post_slug): ! post = Post.objects.get(slug=post_slug)! template_data = {'post': post}! template = "blog/post.html"! ! return render_to_response(! template,! template_data,! context_instance=RequestContext(request)! )

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views.py from django.shortcuts import render_to_response! from django.template import RequestContext! from models import Post! ! def display_post(request, post_slug): ! post = Post.objects.get(slug=post_slug)! template_data = {'post': post}! template = "blog/post.html"! ! return render_to_response(! template,! template_data,! context_instance=RequestContext(request)! )

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views.py from django.shortcuts import render_to_response! from django.template import RequestContext! from models import Post! ! def display_post(request, post_slug): ! post = Post.objects.get(slug=post_slug)! template_data = {'post': post}! template = "blog/post.html"! ! return render_to_response(! template,! template_data,! context_instance=RequestContext(request)! )

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views.py from django.shortcuts import render_to_response! from django.template import RequestContext! from models import Post! ! def display_post(request, post_slug): ! post = Post.objects.get(slug=post_slug)! template_data = {'post': post}! template = "blog/post.html"! ! return render_to_response(! template,! template_data,! context_instance=RequestContext(request)! )

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! ! ! ! {% block title %}{% endblock %}! ! ! ! ! {% block content %}{% endblock %}! ! A base.html template

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A base.html template ! ! ! ! {% block title %}{% endblock %}! ! ! ! ! {% block content %}{% endblock %}! !

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post.html {% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %}

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html template filters

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html

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{% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} post.html template filter

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URLConf’s • Tie it all together! • Route HTTP requests to views • May also capture values

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Root URLConf: urls.py from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! )

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from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! ) Root URLConf: urls.py

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from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! ) Root URLConf: urls.py

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from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! ) Root URLConf: urls.py

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from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! ) Root URLConf: urls.py

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from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! ) Root URLConf: urls.py

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An HTTP Request

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An HTTP Request

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An HTTP Request from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! ) blog/sample-title/

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An HTTP Request from django.conf.urls import patterns, include, url! ! from django.contrib import admin! admin.autodiscover()! ! urlpatterns = patterns('',! url(r'^blog/(?P.+)/$',! 'blog.views.display_post',! name='display_post'),! url(r'^admin/', include(admin.site.urls)),! ) blog/sample-title/

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An HTTP Request def display_post(request, post_slug): ! post = Post.objects.get(slug=post_slug)! template_data = {'post': post}! template = "blog/post.html"! ! return render_to_response(! template,! template_data,! context_instance=RequestContext(request)! ) sample-title

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An HTTP Request {% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} sampleproject/blog/templates/blog/post.html Sample Title

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An HTTP Request {% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} sampleproject/blog/templates/blog/post.html (35, 89)

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An HTTP Request {% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} sampleproject/blog/templates/blog/post.html Lorem Ipsum...

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An HTTP Request {% extends "base.html" %}! ! {% block title %}! {{ post.title }}! {% endblock %}! ! {% block content %}!

{{ post.title }}

!

Published at {{ post.published_at }}

! ! {{ post.content|urlize|linebreaks }}! !

Published on:! {{ post.published_on|date:"M d, Y" }}

! {% endblock %} sampleproject/blog/templates/blog/post.html Nov 3, 2012

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An HTTP Request

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GeoDjango is built on PostgreSQL PostGIS GEOS, GDAL, PROJ

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Want to Learn More? The Official Django Docs are great! https://docs.djangoproject.com

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Thanks! Questions? Brad Montgomery [email protected] @bkmontgomery MEMpy 3rd Monday 6:30 pm-8:30pm @MemphisPython http://mempy.org