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stmt = """
environ = {
        'HTTP_X_REQUESTED_WITH': 'XMLHttpRequest'
}
if 'HTTP_X_REQUESTED_WITH' in environ:
        result = environ['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest'
"""

timeit.timeit(stmt=stmt, number=10000000)
# yields 2.7133121490478516

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from django.http import QueryDict
new_querystring = QueryDict('a=1&b=2', mutable=True)
new_querystring.update({'c': 3, 'a': 4})
new_querystring.urlencode()  # outputs 'a=1&a=4&c=3&b=2'
new_querystring['a'] = 5
new_querystring.urlencode()  # outputs 'a=5&c=3&b=2'

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# I have a known type ... it is X. I should use lazy() then ...
# but SimpleLazyObject "just works", while lazy is obstinate.
from django.utils.functional import lazy, SimpleLazyObject
from collections import namedtuple

X = namedtuple('X', ['a', 'b'])

y = lazy(lambda: X(a=1, b=2), X)
z = SimpleLazyObject(lambda: X(a=1, b=2))

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• Provide middleware;
  • If user is anonymous, look for file in BUILD_DIR
    • If it exists, return it immediately
    • If it doesn't exist, call the view
    • If it doesn't exist and it returns a 2xx, write it to the builder
    • If it doesn't exist and it returns a 3xx, write the 30x.html template to the builder, pointing at the redirect endpoint
    • If it doesn't exist and it returns a 404, write the 404.html to the builder
  • If the user is not anonymous, render the original view, including other middlewares etc.
  • Middleware has an inclusions regex -- see django-moreloaders for regex ideas.
• Provide builders;

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...
$ python manage.py statictemplate > a_static_dir/error_hook.js
...

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from django import template
from django.template.defaultfilters import stringfilter

register = template.Library()

@register.filter
@stringfilter
def pathcss(val):
    parts = list(val.strip('/').split('/'))
    results = []

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>>> from django.utils.functional import lazy
>>> lazy(lambda: None, None)()
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "django/utils/functional.py", line 181, in __wrapper__
    return __proxy__(args, kw)
  File "django/utils/functional.py", line 83, in __init__
    self.__prepare_class__()
  File "django/utils/functional.py", line 95, in __prepare_class__
    for type_ in reversed(resultclass.mro()):

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def runme():
    return 1

def dontrunme():
    return 2

a = {
    'key1': runme,
    'key2': runme,
    'key3': dontrunme,

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• If you type MyModel.<manager>.filter anywhere, you're doing it wrong.
  • Either create a Manager and do it there, or, better yet, use django-model-utils's PassThroughManager and write a proper, chainable queryset.
  • Possibly better than that would just be to have a queries module, which contains functions that return the correct querysets. Seriously, tracking down queries being made is much easier if there's only one place to look.
• If you're doing MyInstance.<related_name>.filter, I still hate you. Fix your manager/queryset or do that queries module I mentioned.
• If you want to do anything to a field on a Form, do it via self.fields[<fieldname>] in the __init__ method. Everything else is crap.
• If you're using a context processor and it touches the database, you'd better make it lazy() or I'll mow you down.
  • Seriously, otherwise it'll do queries for every RequestContext using view, even if it doesn't get used.
• Use django-pdb, django-debug-toolbar and `django-devs

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class MyForm(ModelForm):
    def __init__(self, *args, **kwargs):
        super(MyForm, self).__init__(*args, **kwargs)
        self.fields['myfield'].label = 'hello'
        
    class Meta:
        model = MyModel