Source code for django_tables2.paginators

from django.core.paginator import EmptyPage, Page, PageNotAnInteger, Paginator
from django.utils.translation import gettext as _


[docs]class LazyPaginator(Paginator): """ Implement lazy pagination, preventing any count() queries. By default, for any valid page, the total number of pages for the paginator will be - `current + 1` if the number of records fetched for the current page offset is bigger than the number of records per page. - `current` if the number of records fetched is less than the number of records per page. The number of additional records fetched can be adjusted using `look_ahead`, which defaults to 1 page. If you like to provide a little more extra information on how much pages follow the current page, you can use a higher value. .. note:: The number of records fetched for each page is `per_page * look_ahead + 1`, so increasing the value for `look_ahead` makes the view a bit more expensive. So:: paginator = LazyPaginator(range(10000), 10) >>> paginator.page(1).object_list [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] >>> paginator.num_pages 2 >>> paginator.page(10).object_list [91, 92, 93, 94, 95, 96, 97, 98, 99, 100] >>> paginator.num_pages 11 >>> paginator.page(1000).object_list [9991, 9992, 9993, 9994, 9995, 9996, 9997, 9998, 9999] >>> paginator.num_pages 1000 Usage with `~.SingleTableView`:: class UserListView(SingleTableView): table_class = UserTable table_data = User.objects.all() pagination_class = LazyPaginator Or with `~.RequestConfig`:: RequestConfig(paginate={"paginator_class": LazyPaginator}).configure(table) .. versionadded :: 2.0.0 """ look_ahead = 1 def __init__(self, object_list, per_page, look_ahead=None, **kwargs): self._num_pages = None self._final_num_pages = None if look_ahead is not None: self.look_ahead = look_ahead super().__init__(object_list, per_page, **kwargs) def validate_number(self, number): """Validate the given 1-based page number.""" try: if isinstance(number, float) and not number.is_integer(): raise ValueError number = int(number) except (TypeError, ValueError): raise PageNotAnInteger(_("That page number is not an integer")) if number < 1: raise EmptyPage(_("That page number is less than 1")) return number def page(self, number): # Number might be None, because the total number of pages is not known in this paginator. # If an unknown page is requested, serve the first page. number = self.validate_number(number or 1) bottom = (number - 1) * self.per_page top = bottom + self.per_page # Retrieve more objects to check if there is a next page. look_ahead_items = (self.look_ahead - 1) * self.per_page + 1 objects = list(self.object_list[bottom : top + self.orphans + look_ahead_items]) objects_count = len(objects) if objects_count > (self.per_page + self.orphans): # If another page is found, increase the total number of pages. self._num_pages = number + (objects_count // self.per_page) # In any case, return only objects for this page. objects = objects[: self.per_page] elif (number != 1) and (objects_count <= self.orphans): raise EmptyPage(_("That page contains no results")) else: # This is the last page. self._num_pages = number # For rendering purposes in `table_page_range`, we have to remember the final count self._final_num_pages = number return Page(objects, number, self) def is_last_page(self, number): return number == self._final_num_pages def _get_count(self): raise NotImplementedError count = property(_get_count) def _get_num_pages(self): return self._num_pages num_pages = property(_get_num_pages) def _get_page_range(self): raise NotImplementedError page_range = property(_get_page_range)