countless django paginator for django-rest-framework

paginator.py

import collections

from django.utils import six
from django.core.paginator import PageNotAnInteger, EmptyPage


class Paginator(object):

    def __init__(self, object_list, per_page, orphans=0,
                 allow_empty_first_page=True):
        self.object_list = object_list
        self.per_page = int(per_page)
        self.orphans = int(orphans)
        self.allow_empty_first_page = allow_empty_first_page
        self._num_pages = self._count = None

    def validate_number(self, number):
        """
        Validates the given 1-based page number.
        """
        try:
            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):
        """
        Returns a Page object for the given 1-based page number.
        """
        number = self.validate_number(number)
        bottom = (number - 1) * self.per_page
        top = bottom + self.per_page
        return Page(self.object_list[bottom:top + 1], number, self)


class Page(collections.Sequence):

    def __init__(self, object_list, number, paginator):
        object_length = len(object_list)
        if object_length > paginator.per_page:
            self.object_list = object_list[:object_length - 1]
            self._has_next = True
        else:
            self.object_list = object_list
            self._has_next = False
        # force evaluate queryset to get rid of all function
        # since DRF checks it and then call with queryset.all
        # which will hit db due to different queryset
        self.object_list = list(object_list)
        self.number = number
        self.paginator = paginator

    def __repr__(self):
        return '<Page %s of N/A>' % (self.number,)

    def __len__(self):
        return len(self.object_list)

    def __getitem__(self, index):
        if not isinstance(index, (slice,) + six.integer_types):
            raise TypeError
        # The object_list is converted to a list so that if it was a QuerySet
        # it won't be a database hit per __getitem__.
        if not isinstance(self.object_list, list):
            self.object_list = list(self.object_list)
        return self.object_list[index]

    def has_next(self):
        return self._has_next

    def has_previous(self):
        return self.number > 1

    def has_other_pages(self):
        return self.has_previous() or self.has_next()

    def next_page_number(self):
        if not self._has_next:
            if self.number == 1 and self.allow_empty_first_page:
                pass
            else:
                raise EmptyPage('That page contains no results')
        return self.number + 1

    def previous_page_number(self):
        if self.number < 1:
            raise EmptyPage('That page number is less than 1')
        return self.number - 1