adding static() to urlpatterns only work by appending to the list

Question

I'm pretty sure there is a duplicate lying around, but couldn't find it.

When declaring a urlpatterns in urls.py on dev, I use the following successfully:

urlpatterns = [
    # some routes
]

urlpatterns += static(settings.STATIC_URL, document_root=settings.STATIC_ROOT)

Which understandably, works.

But if I try the following:

urlpatterns = [
    # some routes,
    static(settings.STATIC_URL, document_root=settings.STATIC_ROOT)
]

django server dies complaining:

?: (urls.E004) Your URL pattern [<URLPattern '^static\/(?P<path>.*)$'>] is invalid. Ensure that urlpatterns is a list of path() and/or re_path() instances.

Why aren't the two definitions equivalent? The return of static() should be the same:

return [
    re_path(r'^%s(?P<path>.*)$' % re.escape(prefix.lstrip('/')), view, kwargs=kwargs),
]

And thus valid, but only works if I concatenate the element to the list instead of defining it in the list directly.

Why one method works but not the other?

Answer 1

Well the static function does not return a single url, so you can not add it as a single element to the list. By using +=, you actually append all the elements of the result of the static call to the list.

Recent versions of Python however have special syntax to include an iterable in a list by using the asterisk (*), so it can still be done with:

urlpatterns = [
    # some routes,
    *static(settings.STATIC_URL, document_root=settings.STATIC_ROOT)
]