1.
Advanced Django
Form Usage
by Daniel Greenfeld and Miguel Araujo

2.
Daniel Greenfeld
• pydanny
• Python & Django developer for
Cartwheel Web / RevSys
• Founded django-uni-form
• Does Capoeira
• Lives in Los Angeles with his
Advanced Django Form Usage
http://www.flickr.com/photos/pydanny/4442245488/
Fiancé, Audrey Roy (audreyr)
@pydanny / @maraujop
2

3.
Miguel Araujo
• maraujop
• Freelance Python developer
• Co-lead of django-uni-form
• Does Muay Thai
• Lives in Madrid with his
amazing girlfiend who does
Advanced Django Form Usage
aerospace for a living
@pydanny / @maraujop
• http://maraujop.github.com/
3

4.
Advanced Django Form Usage
@pydanny / @maraujop
Tons of technical content
4

5.
Tons of technical content
• We probably won’t have time for questions
Advanced Django Form Usage
@pydanny / @maraujop
4

6.
Tons of technical content
• We probably won’t have time for questions
• Slides will be posted right after the talk
Advanced Django Form Usage
@pydanny / @maraujop
4

7.
Tons of technical content
• We probably won’t have time for questions
• Slides will be posted right after the talk
• Too much content in the abstract
Advanced Django Form Usage
@pydanny / @maraujop
4

8.
Tons of technical content
• We probably won’t have time for questions
• Slides will be posted right after the talk
• Too much content in the abstract
• Special thanks to:
Advanced Django Form Usage
@pydanny / @maraujop
4

9.
Tons of technical content
• We probably won’t have time for questions
• Slides will be posted right after the talk
• Too much content in the abstract
• Special thanks to:
• Brian Rosner
Advanced Django Form Usage
@pydanny / @maraujop
4

10.
Tons of technical content
• We probably won’t have time for questions
• Slides will be posted right after the talk
• Too much content in the abstract
• Special thanks to:
• Brian Rosner
Advanced Django Form Usage
• James Tauber
@pydanny / @maraujop
4

11.
Tons of technical content
• We probably won’t have time for questions
• Slides will be posted right after the talk
• Too much content in the abstract
• Special thanks to:
• Brian Rosner
Advanced Django Form Usage
• James Tauber
@pydanny / @maraujop
• Frank Wiles
4

12.
Advanced Django Form Usage
@pydanny / @maraujop
Good Form Patterns
Fundamentals of
5

13.
Fundamentals of
Good Form Patterns
• Zen of Python still applies
Advanced Django Form Usage
@pydanny / @maraujop
5

14.
Fundamentals of
Good Form Patterns
• Zen of Python still applies
• import this
Advanced Django Form Usage
@pydanny / @maraujop
5

15.
Fundamentals of
Good Form Patterns
• Zen of Python still applies
• import this
• Spartan programming als0 is important
Advanced Django Form Usage
@pydanny / @maraujop
5

16.
Spartan Programming
• Horizontal complexity
• Vertical complexity (line count)
• Token count
• Character count
• Variables
•
Advanced Django Form Usage
Loops
@pydanny / @maraujop
• Conditionals
http://www.codinghorror.com/blog/2008/07/spartan-programming.html
6

17.
Spartan Programming
• Horizontal complexity
• Vertical complexity (line count)
• Token count
• Character count
• Variables
•
Advanced Django Form Usage
Loops
@pydanny / @maraujop
• Conditionals
http://www.codinghorror.com/blog/2008/07/spartan-programming.html
7

18.
Spartan Programming
• Horizontal complexity
• Vertical complexity (line count)
• Token count
• Character count
• Variables
•
Advanced Django Form Usage
Loops
@pydanny / @maraujop
• Conditionals
http://www.codinghorror.com/blog/2008/07/spartan-programming.html
8

19.
Advanced Django Form Usage
@pydanny / @maraujop
Calling forms the easy way
9

20.
Calling forms the easy way
• Smaller, cleaner code makes our lives better
Advanced Django Form Usage
@pydanny / @maraujop
9

21.
Calling forms the easy way
• Smaller, cleaner code makes our lives better
• Line 5 of the Zen of Python
Advanced Django Form Usage
@pydanny / @maraujop
9

22.
Calling forms the easy way
• Smaller, cleaner code makes our lives better
• Line 5 of the Zen of Python
• Flat is better than nested.
Advanced Django Form Usage
@pydanny / @maraujop
9

23.
Calling forms the easy way
• Smaller, cleaner code makes our lives better
• Line 5 of the Zen of Python
• Flat is better than nested.
• Aim for minimal boilerplate
Advanced Django Form Usage
@pydanny / @maraujop
9

24.
Calling forms the easy way
• Smaller, cleaner code makes our lives better
• Line 5 of the Zen of Python
• Flat is better than nested.
• Aim for minimal boilerplate
Advanced Django Form Usage
• So you can focus on your business logic
@pydanny / @maraujop
9

25.
Enough theory

26.
A Basic Django Form
class MyForm(forms.Form):
name = forms.CharField(_('Name'), required=True)
Advanced Django Form Usage
@pydanny / @maraujop
11

27.
Standard views.py
def my_view(request, template_name='myapp/my_form.html'):
if request.method == 'POST':
form = MyForm(request.POST) # Form #1!
if form.is_valid(): # nested if!
do_x()
return redirect('/')
else:
form = MyForm() # Form #2!
return render(request, template_name, {'form': form})
Advanced Django Form Usage
@pydanny / @maraujop
12

28.
Standard views.py
def my_view(request, template_name='myapp/my_form.html'):
if request.method == 'POST': Form #1
form = MyForm(request.POST) # Form #1!
if form.is_valid(): # nested if!
do_x()
return redirect('/')
else:
form = MyForm() # Form #2!
return render(request, template_name, {'form': form})
Advanced Django Form Usage
@pydanny / @maraujop
12

29.
Standard views.py
def my_view(request, template_name='myapp/my_form.html'):
if request.method == 'POST': Form #1
form = MyForm(request.POST) # Form #1!
if form.is_valid(): # nested if!
do_x()
return redirect('/') Form #2
else:
form = MyForm() # Form #2!
return render(request, template_name, {'form': form})
Advanced Django Form Usage
@pydanny / @maraujop
12

30.
Standard views.py
def my_view(request, template_name='myapp/my_form.html'):
if request.method == 'POST': Form #1
form = MyForm(request.POST) # Form #1!
if form.is_valid(): # nested if!
do_x()
return redirect('/') Form #2
else:
form = MyForm() # Form #2!
return render(request, template_name, {'form': form})
Advanced Django Form Usage
Only 1 nested if, but real code
@pydanny / @maraujop
gets much more complex
12

31.
Standard views.py
def my_view(request, template_name='myapp/my_form.html'):
if request.method == 'POST': Form #1
form = MyForm(request.POST) # Form #1!
if form.is_valid(): # nested if!
do_x()
return redirect('/') Form #2
else:
form = MyForm() # Form #2!
return render(request, template_name, {'form': form})
Advanced Django Form Usage
Only 1 nested if, but real code
@pydanny / @maraujop
gets much more complex Custom business
goes here
12

32.
Standard views.py
def my_view(request, template_name='myapp/my_form.html'):
if request.method == 'POST': Form #1
form = MyForm(request.POST) # Form #1!
if form.is_valid(): # nested if!
do_x()
return redirect('/') Form #2
else:
form = MyForm() # Form #2!
return render(request, template_name, {'form': form})
Advanced Django Form Usage
Only 1 nested if, but real code
@pydanny / @maraujop
gets much more complex Custom business
goes here
12

33.
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Advanced Django Form Usage
@pydanny / @maraujop
Custom business
goes here
13

34.
Single form
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Advanced Django Form Usage
@pydanny / @maraujop
Custom business
goes here
13

35.
Single form
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Advanced Django Form Usage
If no request.POST,
@pydanny / @maraujop
Custom business then instantiated with None
goes here
13

36.
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Advanced Django Form Usage
@pydanny / @maraujop
14

37.
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
• 6 lines of code instead of 9
Advanced Django Form Usage
@pydanny / @maraujop
14

38.
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
• 6 lines of code instead of 9
Advanced Django Form Usage
• 33.3333333333% less code to debug
@pydanny / @maraujop
14

39.
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
• 6 lines of code instead of 9
Advanced Django Form Usage
• 33.3333333333% less code to debug
@pydanny / @maraujop
• One form instantiation
14

40.
Easy views.py
def my_view(request, template_name='myapp/my_form.html'):
# sticks in a POST or renders empty form
form = MyForm(request.POST or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
• 6 lines of code instead of 9
Advanced Django Form Usage
• 33.3333333333% less code to debug
@pydanny / @maraujop
• One form instantiation
• less conditionals == less edge case insanity
14

41.
What about
file uploads?

42.
Easy views.py + files
def my_view(request, template_name='myapp/my_form.html'):
form = MyForm(request.POST or None, request.FILES or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Advanced Django Form Usage
@pydanny / @maraujop
16

43.
Easy views.py + files
def my_view(request, template_name='myapp/my_form.html'):
form = MyForm(request.POST or None, request.FILES or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Request.POST
or None
Advanced Django Form Usage
@pydanny / @maraujop
16

44.
Easy views.py + files
def my_view(request, template_name='myapp/my_form.html'):
form = MyForm(request.POST or None, request.FILES or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Request.POST Request.FILES
or None or None
Advanced Django Form Usage
@pydanny / @maraujop
16

45.
Easy views.py + files
def my_view(request, template_name='myapp/my_form.html'):
form = MyForm(request.POST or None, request.FILES or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Request.POST Request.FILES
or None or None
Advanced Django Form Usage
@pydanny / @maraujop
•
6 lines of code again!
16

46.
Easy views.py + files
def my_view(request, template_name='myapp/my_form.html'):
form = MyForm(request.POST or None, request.FILES or None)
if form.is_valid():
do_x()
return redirect('home')
return render(request, template_name, {'form': form})
Request.POST Request.FILES
or None or None
Advanced Django Form Usage
@pydanny / @maraujop
•
6 lines of code again!
• Code donated by Audrey Roy
16

47.
What about
ModelForms?

48.
Advanced Django Form Usage
@pydanny / @maraujop
pydanny made
up statistics
18

49.
pydanny made
up statistics
• 91% of all Django projects use ModelForms
Advanced Django Form Usage
@pydanny / @maraujop
18

50.
pydanny made
up statistics
• 91% of all Django projects use ModelForms
• 80% ModelForms require trivial logic
Advanced Django Form Usage
@pydanny / @maraujop
18

51.
pydanny made
up statistics
• 91% of all Django projects use ModelForms
• 80% ModelForms require trivial logic
• 20% ModelForms require complicated logic
Advanced Django Form Usage
@pydanny / @maraujop
18

52.
pydanny made
up statistics
• 91% of all Django projects use ModelForms
• 80% ModelForms require trivial logic
• 20% ModelForms require complicated logic
Advanced Django Form Usage
@pydanny / @maraujop
Let’s try and make that easy
18

53.
A Basic ModelForm
class MyModelForm(forms.Form):
class Meta:
model = MyModel
fields = ['name']
Advanced Django Form Usage
@pydanny / @maraujop
19

54.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home')
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
20

55.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel) Form #1
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home')
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
20

56.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel) Form #1
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home') Form #2
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
20

57.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel) Form #1
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home') Form #2
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
Only 1 nested if, but real code
Advanced Django Form Usage
gets much more complex
@pydanny / @maraujop
20

58.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel) Form #1
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home') Form #2
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
Only 1 nested if, but real code
Advanced Django Form Usage
gets much more complex
@pydanny / @maraujop
Custom business
goes here
20

59.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel) Form #1
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home') Form #2
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
Only 1 nested if, but real code
Advanced Django Form Usage
gets much more complex
@pydanny / @maraujop
Custom business
goes here
20

60.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home')
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
21

61.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home')
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
• 12 lines of code
Advanced Django Form Usage
@pydanny / @maraujop
21

62.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home')
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
• 12 lines of code
Advanced Django Form Usage
• Nested conditionals
@pydanny / @maraujop
21

63.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home')
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
• 12 lines of code
Advanced Django Form Usage
• Nested conditionals
@pydanny / @maraujop
• What if we have to handle 3 different submit buttons?
21

64.
Classic views.py for ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/my_model_form.html'):
# I wouldn't call the variable model, because it's an instance of a model, it's confusing
mymodel = get_object_or_404(MyModel, slug=slug)
if request.method == 'POST':
form = MyForm(request, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.day_shown = datetime.datetime.now() # Do any extra model stuff here
mymodel.save()
return redirect('home')
else:
form = MyForm(instance=mymodel)
return render(request, template_name, {'form': form, 'model': mymodel})
• 12 lines of code
Advanced Django Form Usage
• Nested conditionals
@pydanny / @maraujop
• What if we have to handle 3 different submit buttons?
• Watch out for edge case insanity!
21

65.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
22

66.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
Single form
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
22

67.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
Single form
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
Advanced Django Form Usage
Custom business
@pydanny / @maraujop
goes here
22

68.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
Single form
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
If no request.POST,
then instantiated with None
Advanced Django Form Usage
Custom business
@pydanny / @maraujop
goes here So this will fail validation!
22

69.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
23

70.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
• 9 lines of code instead of 12
Advanced Django Form Usage
@pydanny / @maraujop
23

71.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
• 9 lines of code instead of 12
Advanced Django Form Usage
@pydanny / @maraujop
• One conditional
23

72.
easy views.py + ModelForm
def my_model_edit(request, slug=slug, template_name='myapp/
my_model_form.html'):
mymodel = get_object_or_404(MyModel, slug=slug)
form = MyModelForm(request.POST or None, instance=mymodel)
if form.is_valid():
mymodel = form.save()
mymodel.edited_at_djangocon = True
mymodel.save()
return redirect('home')
return render(request, template_name, {'form': form, 'mymodel': mymodel})
• 9 lines of code instead of 12
Advanced Django Form Usage
@pydanny / @maraujop
• One conditional
• clear and succinct code 23

73.
What about new
model instances?

74.
add views.py + ModelForm
def my_model_add(request, template_name='myapp/my_model_form.html'):
form = MyModelForm(request.POST or None)
if form.is_valid():
mymodel = form.save() No need for an
mymodel.added_at_djangocon = True
mymodel.save() instance here
return redirect('home')
return render(request,template_name,{'form': form,'mymodel':mymodel})
Advanced Django Form Usage
@pydanny / @maraujop
25

75.
add views.py + ModelForm
def my_model_add(request, template_name='myapp/my_model_form.html'):
form = MyModelForm(request.POST or None)
if form.is_valid():
mymodel = form.save() No need for an
mymodel.added_at_djangocon = True
mymodel.save() instance here
return redirect('home')
return render(request,template_name,{'form': form,'mymodel':mymodel})
Advanced Django Form Usage
This creates the
@pydanny / @maraujop
model instance.
25

76.
I can make it smaller!
def my_model_tiny_add(request,template_name='myapp/my_model_form.html'):
form = MyModelForm(request.POST or None)
if form.is_valid():
form.save() Not setting defaults here
return redirect('home')
return render(request,template_name,{'form':form,'mymodel':mymodel})
Advanced Django Form Usage
Good practice: Use model field defaults rather
@pydanny / @maraujop
than doing it in your views.
26

77.
How do you test
this stuff?

78.
Advanced Django Form Usage
@pydanny / @maraujop
Please don’t manually
test your forms
28

79.
Please don’t manually
test your forms
• This isn’t a testing talk but...
Advanced Django Form Usage
@pydanny / @maraujop
28

80.
Please don’t manually
test your forms
• This isn’t a testing talk but...
• Forms are the number one thing to test
Advanced Django Form Usage
@pydanny / @maraujop
28

81.
Please don’t manually
test your forms
• This isn’t a testing talk but...
• Forms are the number one thing to test
• Don’t skip on testing them
Advanced Django Form Usage
@pydanny / @maraujop
28

82.
Please don’t manually
test your forms
• This isn’t a testing talk but...
• Forms are the number one thing to test
• Don’t skip on testing them
• Edge case insanity is the thing to fear
Advanced Django Form Usage
@pydanny / @maraujop
28

83.
Django unit tests!
def test_add_package_view(self):
url = reverse('my-url')
response = self.client.get(url)
self.assertEqual(response.status_code, 200)
self.assertTemplateUsed(response, 'package/package_form.html')
for c in Category.objects.all():
self.assertContains(response, c.title)
count = Package.objects.count()
response = self.client.post(url, {
'category': Category.objects.all()[0].pk,
'repo_url': 'http://github.com/django/django',
Advanced Django Form Usage
'slug': 'test-slug',
@pydanny / @maraujop
'title': 'TEST TITLE',
}, follow=True)
self.assertEqual(Package.objects.count(), count + 1)
self.assertContains(response, "Django")
29

84.
Django unit tests!
def test_add_package_view(self):
url = reverse('my-url')
response = self.client.get(url) POSTing a form
self.assertEqual(response.status_code, 200)
self.assertTemplateUsed(response, 'package/package_form.html')
for c in Category.objects.all():
self.assertContains(response, c.title)
count = Package.objects.count()
response = self.client.post(url, {
'category': Category.objects.all()[0].pk,
'repo_url': 'http://github.com/django/django',
Advanced Django Form Usage
'slug': 'test-slug',
@pydanny / @maraujop
'title': 'TEST TITLE',
}, follow=True)
self.assertEqual(Package.objects.count(), count + 1)
self.assertContains(response, "Django")
29

85.
Django unit tests!
def test_add_package_view(self):
url = reverse('my-url')
response = self.client.get(url) POSTing a form
self.assertEqual(response.status_code, 200)
self.assertTemplateUsed(response, 'package/package_form.html')
for c in Category.objects.all():
self.assertContains(response, c.title)
count = Package.objects.count()
follow=True
response = self.client.post(url, {
'category': Category.objects.all()[0].pk,
'repo_url': 'http://github.com/django/django',
Advanced Django Form Usage
'slug': 'test-slug',
@pydanny / @maraujop
'title': 'TEST TITLE',
}, follow=True)
self.assertEqual(Package.objects.count(), count + 1)
self.assertContains(response, "Django")
29

86.
Django unit tests!
def test_add_package_view(self):
url = reverse('my-url')
response = self.client.get(url) POSTing a form
self.assertEqual(response.status_code, 200)
self.assertTemplateUsed(response, 'package/package_form.html')
for c in Category.objects.all():
self.assertContains(response, c.title)
count = Package.objects.count()
follow=True
response = self.client.post(url, {
'category': Category.objects.all()[0].pk,
assertContains is
'repo_url': 'http://github.com/django/django',
Advanced Django Form Usage
'slug': 'test-slug',
your best friend
@pydanny / @maraujop
'title': 'TEST TITLE',
}, follow=True)
self.assertEqual(Package.objects.count(), count + 1)
self.assertContains(response, "Django")
29

87.
Can we
change non-required
to required?

88.
non-required to required
• Your model fields are non-required
• but you want the form fields to be required
Advanced Django Form Usage
@pydanny / @maraujop
31

89.
A basic Django models.py
class MyModel(models.Model):
name = models.CharField(_('Name'), max_length=50, blank=True, null=True)
age = models.IntegerField(_('Age in years'), blank=True, null=True)
profession = models.CharField(_('Profession'),
max_length=100, blank=True, null=True)
bio = models.TextField(_('Bio'), blank=True, null=True)
Advanced Django Form Usage
@pydanny / @maraujop
32

90.
Classic forms.py overload
class MyModelTooMuchTypingForm(forms.ModelForm):
""" I've done this and it sucks
hard to debug and too much duplication
"""
name = forms.CharField(_('Name'), max_length=50, required=True)
age = forms.IntegerField(_('Age in years'), required=True)
profession = forms.CharField(_('Profession'), required=True)
bio = forms.TextField(_('Bio'), required=True)
class Meta:
model = MyModel
Advanced Django Form Usage
@pydanny / @maraujop
33

91.
Classic forms.py overload
class MyModelTooMuchTypingForm(forms.ModelForm):
""" I've done this and it sucks
hard to debug and too much duplication
"""
name = forms.CharField(_('Name'), max_length=50, required=True)
age = forms.IntegerField(_('Age in years'), required=True)
profession = forms.CharField(_('Profession'), required=True)
bio = forms.TextField(_('Bio'), required=True)
class Meta:
model = MyModel
Advanced Django Form Usage
@pydanny / @maraujop
class MyModel(models.Model):
name = models.CharField(_('Name'), max_length=50, blank=True, null=True)
age = models.IntegerField(_('Age in years'), blank=True, null=True)
profession = models.CharField(_('Profession'), max_length=100, blank=True, null=True)
bio = models.TextField(_('Bio'), blank=True, null=True)
33

92.
Classic forms.py overload
class MyModelTooMuchTypingForm(forms.ModelForm):
""" I've done this and it sucks
hard to debug and too much duplication
"""
name = forms.CharField(_('Name'), max_length=50, required=True)
age = forms.IntegerField(_('Age in years'), required=True)
profession = forms.CharField(_('Profession'), required=True)
bio = forms.TextField(_('Bio'), required=True)
class Meta: Nearly duplicated code
model = MyModel
Advanced Django Form Usage
@pydanny / @maraujop
class MyModel(models.Model):
name = models.CharField(_('Name'), max_length=50, blank=True, null=True)
age = models.IntegerField(_('Age in years'), blank=True, null=True)
profession = models.CharField(_('Profession'), max_length=100, blank=True, null=True)
bio = models.TextField(_('Bio'), blank=True, null=True)
33

93.
Classic forms.py overload
class MyModelTooMuchTypingForm(forms.ModelForm):
""" I've done this and it sucks
hard to debug and too much duplication
"""
name = forms.CharField(_('Name'), max_length=50, required=True)
age = forms.IntegerField(_('Age in years'), required=True)
profession = forms.CharField(_('Profession'), required=True)
bio = forms.TextField(_('Bio'), required=True)
class Meta: Nearly duplicated code
model = MyModel
Advanced Django Form Usage
@pydanny / @maraujop
class MyModel(models.Model):
name = models.CharField(_('Name'), max_length=50, blank=True, null=True)
age = models.IntegerField(_('Age in years'), blank=True, null=True)
profession = models.CharField(_('Profession'), max_length=100, blank=True, null=True)
bio = models.TextField(_('Bio'), blank=True, null=True)
33

94.
Better forms.py overload
class MyModelForm(forms.ModelForm):
""" Much better and you are extending, not copy/pasting """
def __init__(self):
super(MyModelForm, self).__init__(*args, **kwargs)
self.fields['name'].required = True
self.fields['age'].required = True
self.fields['profession'].required = True
self.fields['profession'].help_text = _("Hi professor")
Advanced Django Form Usage
class Meta:
Fields are in a dict-like object
@pydanny / @maraujop
model = MyModel
34

95.
Try it with inheritance!
class BaseEmailForm(forms.Form):
email = forms.EmailField(_('Email'))
confirm_email = forms.EmailField(_('Email 2'))
class ContactForm(BaseEmailForm):
message = forms.CharField(_('Message'))
def __init__(self):
super(ContactForm, self).__init__(*args, **kwargs)
self.fields['confirm_email'].label = _('Confirm your email')
self.fields['confirm_email'].description = _('We want to be absolutely
certain we have your correct email address.')
Advanced Django Form Usage
@pydanny / @maraujop
35

96.
Add dynamic fields
to a form

97.
Dynamically adding fields
to a form
def my_view(request, template_name='myapp/my_model_form.html'):
form = MyModelForm(request.POST or None)
# Let's add a field on the go, needs to be done before validating it
form.fields['favorite_color'] = forms.ChoiceField(
label = "Which is your favorite color from these?",
choices = (('blue', 'blue'), ('red', 'red'), ('green', 'green')),
widget = forms.RadioSelect,
required = True,
)
if form.is_valid():
# Let's get user's favorite color,
# you can do whatever you want with it
favorite_color = form.cleaned_data['favorite_color']
Advanced Django Form Usage
form.save()
@pydanny / @maraujop
return redirect('home')
return render(request, template_name, {'form': form})
37

98.
Dynamically adding fields
to a form
def my_view(request, template_name='myapp/my_model_form.html'): Form dictionary
form = MyModelForm(request.POST or None) of fields
# Let's add a field on the go, needs to be done before validating it
form.fields['favorite_color'] = forms.ChoiceField(
label = "Which is your favorite color from these?",
choices = (('blue', 'blue'), ('red', 'red'), ('green', 'green')),
widget = forms.RadioSelect,
required = True,
)
if form.is_valid():
# Let's get user's favorite color,
# you can do whatever you want with it
favorite_color = form.cleaned_data['favorite_color']
Advanced Django Form Usage
form.save()
@pydanny / @maraujop
return redirect('home')
return render(request, template_name, {'form': form})
37

99.
Dynamically adding fields
to a form
def my_view(request, template_name='myapp/my_model_form.html'): Form dictionary
form = MyModelForm(request.POST or None) of fields
# Let's add a field on the go, needs to be done before validating it
form.fields['favorite_color'] = forms.ChoiceField(
label = "Which is your favorite color from these?",
choices = (('blue', 'blue'), ('red', 'red'), ('green', 'green')),
widget = forms.RadioSelect,
required = True,
)
Fields have to be added
before the form.is_valid
if form.is_valid():
# Let's get user's favorite color,
# you can do whatever you want with it
favorite_color = form.cleaned_data['favorite_color']
method is checked.
Advanced Django Form Usage
form.save()
@pydanny / @maraujop
return redirect('home')
return render(request, template_name, {'form': form})
37

100.
Can’t we just pass in a
list of fields into a form
from a view?

101.
Constructor overrides forms.py
class MyModelForm(forms.ModelForm):
def __init__(self, *args, **kwargs):
extra = kwargs.pop('extra')
super(UserCreationForm, self).__init__(*args, **kwargs)
for i, question in enumerate(extra):
self.fields['custom_%s' % i] = forms.CharField(label=question)
def extra_fields(self): looping over
"""
Returns a tuple (question, answer)
‘extra’ iterable
Advanced Django Form Usage
"""
@pydanny / @maraujop
for name, value in self.cleaned_data.items():
if name.startswith('custom_'):
yield (self.fields[name].label, value)
39

102.
Constructor overrides views.py
def my_view(request, template_name='myapp/my_model_form.html'):
form = MyModelForm(request.POST or None,
extra=["What's your pet's name?"])
Passing in a list
if form.is_valid():
# We can gather extra fields data doing
of form field
for (question, answer) in form.extra_fields(): titles
save_answer(request, question, answer)
form.save()
return redirect('home')
Advanced Django Form Usage
@pydanny / @maraujop
return render(request, template_name, {'form': form})
40

103.
I need a formset

104.
formsets.py
class ItemFormSet(BaseFormSet):
def __init__(self, numberItems, *args, **kwargs):
super(ItemFormSet, self).__init__(*args, **kwargs)
self.numberItems = numberItems
def clean(self):
# Don't bother validating the formset
# unless each form is valid on its own
if any(self.errors):
return
for form in self.forms:
Advanced Django Form Usage
if not form.cleaned_data['your_choice'] == 'mod_wsgi':
@pydanny / @maraujop
raise ValidationError(u'mod_wsgi is the way to go!')
42

105.
formsets.py
class ItemFormSet(BaseFormSet):
def __init__(self, numberItems, *args, **kwargs):
super(ItemFormSet, self).__init__(*args, **kwargs)
self.numberItems = numberItems
def clean(self):
Forms must have
# Don't bother validating the formset
‘your_choice’ field that
# unless each form is valid on its own
if any(self.errors):
return only accepts “mod_wsgi”
for form in self.forms:
Advanced Django Form Usage
if not form.cleaned_data['your_choice'] == 'mod_wsgi':
@pydanny / @maraujop
raise ValidationError(u'mod_wsgi is the way to go!')
42

106.
views.py
from django.forms.models import formset_factory
def wsgi_form_view(request):
WsgiFormset = formset_factory(ExampleForm, extra=5,
formset=ItemFormSet)
formset = WsgiFormset(bogus_number, request.POST,
request.FILES)
Advanced Django Form Usage
@pydanny / @maraujop
Truncated formset view
43

107.
Lets do
programmatic layout
of forms

108.
Things I want python
to describe in forms
• Different fieldsets within the same form
• Various buttons
• submit
• reset
Advanced Django Form Usage
@pydanny / @maraujop
45

109.
Advanced Django Form Usage
@pydanny / @maraujop
django-uni-form
46

110.
Programmatic layouts
class ExampleForm(forms.Form):
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout(
Fieldset(
'first arg is the legend of the fieldset',
'like_website',
'favorite_number',
),
Fieldset(
'second arg is the legend of the fieldset',
'favorite_color',
'favorite_food',
Advanced Django Form Usage
)
@pydanny / @maraujop
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
)
)
return super(ExampleForm, 47
self).__init__(*args, **kwargs)

111.
Programmatic layouts
from uni_form.helpers import FormHelper, Submit, Reset
from uni_form.helpers import Fieldset, ButtonHolder, Layout
class ExampleForm(forms.Form):
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout(
Fieldset(
'first arg is the legend of the fieldset',
'like_website',
'favorite_number',
),
Fieldset(
'second arg is the legend of the fieldset',
'favorite_color',
'favorite_food',
Advanced Django Form Usage
)
@pydanny / @maraujop
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
)
)
return super(ExampleForm, 47
self).__init__(*args, **kwargs)

112.
Programmatic layouts
from uni_form.helpers import FormHelper, Submit, Reset
from uni_form.helpers import Fieldset, ButtonHolder, Layout
class ExampleForm(forms.Form): FormHelper
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout(
Fieldset(
'first arg is the legend of the fieldset',
'like_website',
'favorite_number',
),
Fieldset(
'second arg is the legend of the fieldset',
'favorite_color',
'favorite_food',
Advanced Django Form Usage
)
@pydanny / @maraujop
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
)
)
return super(ExampleForm, 47
self).__init__(*args, **kwargs)

113.
Programmatic layouts
from uni_form.helpers import FormHelper, Submit, Reset
from uni_form.helpers import Fieldset, ButtonHolder, Layout
class ExampleForm(forms.Form): FormHelper
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout( Layout
Fieldset(
'first arg is the legend of the fieldset',
'like_website',
'favorite_number',
),
Fieldset(
'second arg is the legend of the fieldset',
'favorite_color',
'favorite_food',
Advanced Django Form Usage
)
@pydanny / @maraujop
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
)
)
return super(ExampleForm, 47
self).__init__(*args, **kwargs)

114.
Programmatic layouts
from uni_form.helpers import FormHelper, Submit, Reset
from uni_form.helpers import Fieldset, ButtonHolder, Layout
class ExampleForm(forms.Form): FormHelper
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout( Layout
Fieldset(
'first arg is the legend of the fieldset',
Fieldset 'like_website',
'favorite_number',
),
Fieldset(
'second arg is the legend of the fieldset',
'favorite_color',
'favorite_food',
Advanced Django Form Usage
)
@pydanny / @maraujop
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
)
)
return super(ExampleForm, 47
self).__init__(*args, **kwargs)

115.
Programmatic layouts
from uni_form.helpers import FormHelper, Submit, Reset
from uni_form.helpers import Fieldset, ButtonHolder, Layout
class ExampleForm(forms.Form): FormHelper
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout( Layout
Fieldset(
'first arg is the legend of the fieldset',
Fieldset 'like_website',
'favorite_number',
),
Fieldset(
'second arg is the legend of the fieldset',
'favorite_color', Button
'favorite_food',
Holder
Advanced Django Form Usage
)
@pydanny / @maraujop
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
)
)
return super(ExampleForm, 47
self).__init__(*args, **kwargs)

116.
Programmatic layouts
from uni_form.helpers import FormHelper, Submit, Reset
from uni_form.helpers import Fieldset, ButtonHolder, Layout
class ExampleForm(forms.Form): FormHelper
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout( Layout
Fieldset(
'first arg is the legend of the fieldset',
Fieldset 'like_website',
'favorite_number',
),
Fieldset(
'second arg is the legend of the fieldset',
Button 'favorite_color', Button
'favorite_food',
Holder
Advanced Django Form Usage
)
@pydanny / @maraujop
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
)
)
return super(ExampleForm, 47
self).__init__(*args, **kwargs)

117.
renders as divs
{% load uni_form_tags %}
{% uni_form my_form my_form.helper %}
Renders the HTML form
with buttons and everything
wrapped in a fieldset.
Advanced Django Form Usage
@pydanny / @maraujop
48

118.
Sample output
<form action="#" class="uniForm">
<fieldset class="inlineLabels">
<div class="ctrlHolder">
<label for="name">Name</label>
<input type="text" id="name" name="name" value="" size="35" class="textInput"/>
</div>
<div class="ctrlHolder">
<label for="email">Email</label>
<input type="text" id="email" name="email" value="" size="35" class="textInput"/>
</div>
<div class="ctrlHolder">
<label for="comment">Comment</label>
<textarea id="comment" name="comment" rows="25" cols="25"></textarea>
</div>
<div class="buttonHolder">
<label for="tos" class="secondaryAction"><input type="checkbox" id="tos" name="tos"/>
Advanced Django Form Usage
I agree to the <a href="#">terms of service</a></label>
<button type="submit" class="primaryAction">Post comment</button>
@pydanny / @maraujop
</div>
</fieldset>
</form>
49

119.
django-uni-form
• Programmatic layout
• Div based forms
• Section 508 compliant
• Fully customizable templates
Advanced Django Form Usage
• http://django-uni-form.rtfd.org
@pydanny / @maraujop
50

120.
What about
HTML5 Fields?

121.
django-floppyforms
• by Bruno Renie @brutasse
• HTML5 Widgets
• Fully customizable templates
• Plays nice with django-uni-form
Advanced Django Form Usage
@pydanny / @maraujop
52

122.
Easy to use!
import floppyforms as forms
class ExampleForm(forms.Form):
username = forms.CharField(
label='',
widget = forms.TextInput(
attrs={'placeholder': '@johndoe'},
),
)
• Django’s widget parameter attrs expects a dictionary
Advanced Django Form Usage
@pydanny / @maraujop
• Replaces the normal widgets with HTML5 ones
53

123.
Customizable widgets
import floppyforms as forms
class OtherEmailInput(forms.EmailInput):
template_name = 'path/to/other_email.html'
forms.py
<input type="email"
name="{{ name }}"
id="{{ attrs.id }}"
Advanced Django Form Usage
placeholder="john@example.com"
@pydanny / @maraujop
{% if value %}value="{{ value }}"{% endif %}>
path/to/other_email.html
54

124.
Can you combine
django-uni-form and
django-floppyforms?

125.
django-uni-form +
django-floppyforms
=
AWESOME POWER

126.
They get along well
class ListFriendsForm(forms.Form):
username = forms.CharField(
widget = forms.TextInput(
attrs={'placeholder': '@maraujop'}, No changes or
)
),
special code needed
def __init__(self, *args, **kwargs):
self.helper = FormHelper()
self.helper.layout = Layout(
Div(
'username',
)
ButtonHolder(
Submit('submit', 'Submit', css_class='button white')
Advanced Django Form Usage
)
@pydanny / @maraujop
)
return super(ExampleForm, self).__init__(*args, **kwargs)
57

127.
Forms refactor
Django 1.4

128.
Advanced Django Form Usage
@pydanny / @maraujop
What we are getting in 1.4
59

129.
What we are getting in 1.4
• Form rendering will use templates instead
of HTML in Python
Advanced Django Form Usage
@pydanny / @maraujop
59

130.
What we are getting in 1.4
• Form rendering will use templates instead
of HTML in Python
• Template based widgets
Advanced Django Form Usage
@pydanny / @maraujop
59

131.
What we are getting in 1.4
• Form rendering will use templates instead
of HTML in Python
• Template based widgets
• Template based form layout
Advanced Django Form Usage
@pydanny / @maraujop
59

132.
Advanced Django Form Usage
@pydanny / @maraujop
forms refactor and
django-uni-form
60

133.
forms refactor and
django-uni-form
• forms refactor layout “lives” in templates
Advanced Django Form Usage
@pydanny / @maraujop
60

134.
forms refactor and
django-uni-form
• forms refactor layout “lives” in templates
• django-uni-form layout “lives” in python
Advanced Django Form Usage
@pydanny / @maraujop
60

135.
forms refactor and
django-uni-form
• forms refactor layout “lives” in templates
• django-uni-form layout “lives” in python
• Different approaches, same objective
Advanced Django Form Usage
@pydanny / @maraujop
60

136.
Give me a way to
create custom
form fields

137.
The docs on custom fields
“Its only requirements are that it implement
a clean() method and that its __init__()
method accept the core arguments
mentioned above (required, label, initial,
widget, help_text).”
Advanced Django Form Usage
@pydanny / @maraujop
62

138.
The docs on custom fields
“Its only requirements are that it implement
a clean() method and that its __init__()
method accept the core arguments
mentioned above (required, label, initial,
widget, help_text).”
Advanced Django Form Usage
The docs seem to be wrong
@pydanny / @maraujop
62

139.
How it really works
You don’t need to implement “clean”
You do need to implement:
• required
• widget • error_messages
• label • show_hidden_initial
Advanced Django Form Usage
• help_text • validators
@pydanny / @maraujop
• initial • localize
63

140.
How the heck then do I
actually add a custom
form field?!?

141.
Advanced Django Form Usage
@pydanny / @maraujop
validation work?
How does form
65

142.
fields.py
class AMarkField(forms.Field):
widget = TextInput
default_error_messages = {
'not_an_a': _(u'you can only input A here! damn!'),
}
def __init__(self, **kwargs):
super(AMarkField, self).__init__(**kwargs)
def to_python(self, value):
if value in validators.EMPTY_VALUES:
Only accepts upper
return None
case A as input
Advanced Django Form Usage
if value != 'A':
@pydanny / @maraujop
raise ValidationError(self.error_messages['not_an_a'])
return value
66

143.
Not DRY
class MyModelForm(forms.ModelForm):
mark = CharField()
def clean_mark(self):
mark_value = self.cleaned_data['mark']
if mark_value is not None or mark_value.upper() != 'A':
raise ValidationError(_(u'Only input A here!'))
return mark_value
class ExampleForm(forms.Form):
mark = CharField()
def clean_mark(self):
Advanced Django Form Usage
mark_value = self.cleaned_data['mark']
@pydanny / @maraujop
if mark_value is not None or mark_value.upper() != 'A':
raise ValidationError(_(u'Only input A here!'))
return mark_value
67

144.
I want a custom field
that validates JSON

145.
The JSON field
class JSONField(forms.Field):
default_error_messages = {
'invalid': 'This is not valid JSON string'
}
def to_python(self, value):
if value in validators.EMPTY_VALUES:
return None
try:
json = simplejson.loads(value)
Advanced Django Form Usage
except ValueError:
@pydanny / @maraujop
raise ValidationError(self.error_messages['invalid'])
return json
69

146.
I want a custom
widget that handles
multiple widgets

147.
widgets.py
from django.forms.extras.widgets import MultiWidget
class AddressWidget(MultiWidget):
def __init__(self, attrs=None):
widgets = (TextInput, TextInput)
super(AddressWidget, self).__init__(widgets, attrs)
def decompress(self, value):
"""
If called, value is a string should return a list
"""
Advanced Django Form Usage
if value:
# parse stuff and return a list
@pydanny / @maraujop
return value.split()
return [None, None]
71

148.
widgets.py
from django.forms.extras.widgets import MultiWidget
class AddressWidget(MultiWidget): Two TextInput
def __init__(self, attrs=None): widgets!!!
widgets = (TextInput, TextInput)
super(AddressWidget, self).__init__(widgets, attrs)
def decompress(self, value):
"""
If called, value is a string should return a list
"""
Advanced Django Form Usage
if value:
# parse stuff and return a list
@pydanny / @maraujop
return value.split()
return [None, None]
71

149.
widgets.py
from django.forms.extras.widgets import MultiWidget
class AddressWidget(MultiWidget): Two TextInput
def __init__(self, attrs=None): widgets!!!
widgets = (TextInput, TextInput)
super(AddressWidget, self).__init__(widgets, attrs)
def decompress(self, value):
"""
If called, value is a string should return a list
"""
Advanced Django Form Usage
if value:
# parse stuff and return a list
@pydanny / @maraujop
return value.split()
Called when a form with
return [None, None] MultiWidget is passed initial
or instance values
71

150.
fields.py
class AddressField(forms.Field):
self.widget = AddressWidget
def to_python(self, value):
# Already gets a Python list
return value
isinstance(["921 SW Sixth Avenue", "Portland"], list)
Advanced Django Form Usage
@pydanny / @maraujop
72

151.
fields.py
class AddressField(forms.Field):
self.widget = AddressWidget
def to_python(self, value):
# Already gets a Python list
return value
isinstance(["921 SW Sixth Avenue", "Portland"], list)
class ExampleForm(object):
forms.CharField(widget=AddressWidget)
Advanced Django Form Usage
isinstance("921 SW Sixth Avenue, Portland", str)
@pydanny / @maraujop
72

152.
Give me a MultiValue,
MultiWidget field

153.
MultiValue, MultiWidget Field
class AlternativeAddressField(forms.MultiValueField):
widget = AddressWidget
def __init__(self, *args, **kwargs):
fields = (forms.CharField(), forms.CharField())
super(AlternativeAddressField, self).__init__(fields,
*args, **kwargs)
def compress(self, data_list):
return data_list
Advanced Django Form Usage
@pydanny / @maraujop
74

154.
MultiValue, MultiWidget Field
class AlternativeAddressField(forms.MultiValueField):
widget = AddressWidget
def __init__(self, *args, **kwargs):
fields = (forms.CharField(), forms.CharField())
super(AlternativeAddressField, self).__init__(fields,
*args, **kwargs)
def compress(self, data_list):
return data_list
• Clean does not work in the standard way
Advanced Django Form Usage
@pydanny / @maraujop
74

155.
MultiValue, MultiWidget Field
class AlternativeAddressField(forms.MultiValueField):
widget = AddressWidget
def __init__(self, *args, **kwargs):
fields = (forms.CharField(), forms.CharField())
super(AlternativeAddressField, self).__init__(fields,
*args, **kwargs)
def compress(self, data_list):
return data_list
• Clean does not work in the standard way
• Every field validated with its corresponding widget value
Advanced Django Form Usage
@pydanny / @maraujop
74

156.
MultiValue, MultiWidget Field
class AlternativeAddressField(forms.MultiValueField):
widget = AddressWidget
def __init__(self, *args, **kwargs):
fields = (forms.CharField(), forms.CharField())
super(AlternativeAddressField, self).__init__(fields,
*args, **kwargs)
def compress(self, data_list):
return data_list
• Clean does not work in the standard way
• Every field validated with its corresponding widget value
Advanced Django Form Usage
•
@pydanny / @maraujop
Beware! run_validator does run but validate is called
74

157.
MultiValue, MultiWidget Field
class AlternativeAddressField(forms.MultiValueField):
widget = AddressWidget
def __init__(self, *args, **kwargs):
fields = (forms.CharField(), forms.CharField())
super(AlternativeAddressField, self).__init__(fields,
*args, **kwargs)
def compress(self, data_list):
return data_list
• Clean does not work in the standard way
• Every field validated with its corresponding widget value
Advanced Django Form Usage
•
@pydanny / @maraujop
Beware! run_validator does run but validate is called
Django Ticket #14184
74

158.
Validators with Multi-Field
class AlternativeAddressField(forms.MultiValueField):
widget = AddressWidget
def __init__(self, *args, **kwargs):
fields = (forms.CharField(), forms.CharField())
super(AlternativeAddressField, self).__init__(fields,
*args, **kwargs)
def validate(self, value):
self._run_validators(value)
def compress(self, data_list):
Advanced Django Form Usage
return data_list
@pydanny / @maraujop
75

159.
How about custom
widget output?

160.
Advanced Django Form Usage
@pydanny / @maraujop
Custom Widget Output
So Easy!
77

161.
def render(self, name, value, attrs=None):
Custom Widget Output
# HTML to be added to the output
widget_labels = [
'<label for="id_%s">Address: </label>',
'<label for="id_%s">Number: </label>'
]
if self.is_localized:
for widget in self.widgets:
widget.is_localized = self.is_localized
# value is a list of values, each corresponding to a widget
So Easy!
# in self.widgets.
if not isinstance(value, list):
value = self.decompress(value)
output = []
final_attrs = self.build_attrs(attrs)
id_ = final_attrs.get('id', None)
for i, widget in enumerate(self.widgets):
try:
widget_value = value[i]
except IndexError:
widget_value = None
if id_:
Advanced Django Form Usage
final_attrs = dict(final_attrs, id='%s_%s' % (id_, i))
# Adding labels
@pydanny / @maraujop
output.append(widget_labels[i] % ('%s_%s' % (name, i)))
output.append(widget.render(name + '_%s' % i, widget_value, final_attrs))
return mark_safe(self.format_output(output))
77

162.
def render(self, name, value, attrs=None):
Custom Widget Output
# HTML to be added to the output
widget_labels = [
'<label for="id_%s">Address: </label>',
'<label for="id_%s">Number: </label>'
]
if self.is_localized:
for widget in self.widgets:
widget.is_localized = self.is_localized
# value is a list of values, each corresponding to a widget
So Easy!
# in self.widgets.
if not isinstance(value, list):
value = self.decompress(value)
output = []
final_attrs = self.build_attrs(attrs)
id_ = final_attrs.get('id', None)
for i, widget in enumerate(self.widgets):
try:
widget_value = value[i]
except IndexError:
widget_value = None
if id_:
Advanced Django Form Usage
final_attrs = dict(final_attrs, id='%s_%s' % (id_, i))
# Adding labels
@pydanny / @maraujop
output.append(widget_labels[i] % ('%s_%s' % (name, i)))
output.append(widget.render(name + '_%s' % i, widget_value, final_attrs))
return mark_safe(self.format_output(output))
77

163.
Can’t you make it
easier to understand?

164.
Problems with Custom
Widget Output
• Overring render means indepth knowledge
• Hard to do custom output with built-in widgets
• You can’t call super.render and customize easily
• Templates? Open Ticket #15667
Advanced Django Form Usage
@pydanny / @maraujop
79

165.
Not in Lawrence
Kansas anymore

166.
Problems with Custom
Widget Output
• Oldest ticket in Django is related to forms
(#23)
• ComboField is broken
• Validators are thought to validate simple values
Advanced Django Form Usage
because of the way run_validators is coded
@pydanny / @maraujop
81

167.
HTML5 tickets
• Ticket #16304
• Ticket #16630
• Just use django-floppyforms
Advanced Django Form Usage
@pydanny / @maraujop
82

168.
Validators
• Imagine you have an input that get a list of emails seperated
by spaces
• Your widget returns: [“a@example.com”, “b@example.com”]
• You want to run validators on all of them
•
Advanced Django Form Usage
There is an EmailValidator
@pydanny / @maraujop
83

169.
MultiValidator
class MultiValidator(object):
def __init__(self, validators):
self.validators = validators
def __call__(self, data_list):
errors = []
for value in data_list:
for validator in self.validators:
try:
validator(value)
except ValidationError, e:
Advanced Django Form Usage
if hasattr(e, 'code'):
errors.append("FiXED MESSAGE")
@pydanny / @maraujop
raise ValidationError(errors)
84

170.
Amazing stuff
• Ticket #27 reported by Adrian Holovaty
• Single form field for multiple database fields
Advanced Django Form Usage
@pydanny / @maraujop
85

171.
Fin

172.
Advanced Django Form Usage
@pydanny / @maraujop
This has been
incredible
87

173.
This has been
incredible
• We’ve just scratched the surface
Advanced Django Form Usage
@pydanny / @maraujop
87

174.
This has been
incredible
• We’ve just scratched the surface
• Keep your code clean - or you’ll regret it
Advanced Django Form Usage
@pydanny / @maraujop
87