Short Python tips, sometimes with a Django bent, sometimes without unit tests.

autodunder.py

def _autofmthelper(name, fmt, postprocess=None):
    def fmtfunc(self):
        result = fmt.format(self=self)
        if postprocess is not None:
            result = postprocess(self, result)
        return result
    fmtfunc.__name__ = name
    return fmtfunc

def autounicode(fmt):
    """ Returns a simple ``__unicode__`` function::

        >>> class Person(object):
        ...     name = "Alex"
        ...     __unicode__ = autounicode("{self.name}")
        ...
        >>> unicode(Person())
        u'Alex'
        >>>
        """
    return _autofmthelper("__unicode__", unicode(fmt))

def autostr(fmt):
    """ Returns a simple ``__str__`` function::

        >>> class Person(object):
        ...     name = "Alex"
        ...     __str__ = autostr("{self.name}")
        ...
        >>> str(Person())
        'Alex'
        >>>
        """
    fmt = str(fmt)
    return _autofmthelper("__str__", str(fmt))

def autorepr(fmt):
    """ Returns a simple ``__repr__`` function::

        >>> class Person(object):
        ...     name = "Alex"
        ...     __repr__ = autorepr("name={self.name!r}")
        ...
        >>> repr(Person())
        "<__main__.Person name='Alex' at 0x...>"
        >>>
        """
    return _autofmthelper("__repr__", str(fmt), lambda self, result: (
        "<%s.%s %s at 0x%x>" %(
            self.__class__.__module__,
            self.__class__.__name__,
            result,
            id(self),
        )
    ))

nested_urls.py

# Django URLs can be nested within one file!
# Have a bunch of URLs with a verbose prefix? Group them together!

# boo bad and ugly and not fun:
urlpatterns = patterns(''
    url('^(?P<wikipage_title_slug>\w+)-(?P<wikipage_id>\w+)/history$', …),
    url('^(?P<wikipage_title_slug>\w+)-(?P<wikipage_id>\w+)/edit$', …),
    url('^(?P<wikipage_title_slug>\w+)-(?P<wikipage_id>\w+)/discuss$', …),
    url('^(?P<wikipage_title_slug>\w+)-(?P<wikipage_id>\w+)/permissions$', …),
)

# yay happy and pretty and fun:
urlpatterns = patterns(''
    url('^(?P<wikipage_title_slug>\w+)-(?P<wikipage_id>\w+)/', include(patterns('',
        url('^history$', …),
        url('^edit$', …),
        url('^discuss$', …),
        url('^permissions$', …),
    )),
)

quote_component.py

def quote_component(s):
    """ Returns a strint suitable for use as any component in a URL::

            >>> quote_component("/ +%#")
            '%2F%20%2B%25%23'

        Note that this is especially useful with Django's ``reverse()``, which
        does not automatically quote anything::
        
            reverse("my-view", kwargs={"name": quote_component(person.name)})
        """
    return urllib.quote(smart_str(s), safe="-_.!~*'()")

slug_property.py

from django.template.defaultfilters import slugify

def slug_property(attr):
    """ ``property`` which returns a slugified version of ``attr``. Useful
        with Models::

            >>> class WikiPage(m.Model):
            ...    title = m.CharField(max_length=64)
            ...    title_slug = slug_property("title")
            ...
            >>> p = WikiPage(title="Hello, World!")
            >>> p.title_slug
            'hello-world'
        """

    def slug_property_helper(self):
        return slugify(getattr(self, attr))
    return property(slug_property_helper)