import collections.abc
import inspect
import warnings
from math import ceil
from django.utils.functional import cached_property
from django.utils.inspect import method_has_no_args
from django.utils.translation import gettext_lazy as _
class UnorderedObjectListWarning(RuntimeWarning):
pass
class InvalidPage(Exception):
pass
class PageNotAnInteger(InvalidPage):
pass
class EmptyPage(InvalidPage):
pass
class Paginator:
# Translators: String used to replace omitted page numbers in elided page
# range generated by paginators, e.g. [1, 2, '…', 5, 6, 7, '…', 9, 10].
ELLIPSIS = _('…')
def __init__(self, object_list, per_page, orphans=0,
allow_empty_first_page=True):
self.object_list = object_list
self._check_object_list_is_ordered()
self.per_page = int(per_page)
self.orphans = int(orphans)
self.allow_empty_first_page = allow_empty_first_page
def __iter__(self):
for page_number in self.page_range:
yield self.page(page_number)
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'))
if number > self.num_pages:
if number == 1 and self.allow_empty_first_page:
pass
else:
raise EmptyPage(_('That page contains no results'))
return number
def get_page(self, number):
"""
Return a valid page, even if the page argument isn't a number or isn't
in range.
"""
try:
number = self.validate_number(number)
except PageNotAnInteger:
number = 1
except EmptyPage:
number = self.num_pages
return self.page(number)
def page(self, number):
"""Return 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
if top + self.orphans >= self.count:
top = self.count
return self._get_page(self.object_list[bottom:top], number, self)
def _get_page(self, *args, **kwargs):
"""
Return an instance of a single page.
This hook can be used by subclasses to use an alternative to the
standard :cls:`Page` object.
"""
return Page(*args, **kwargs)
@cached_property
def count(self):
"""Return the total number of objects, across all pages."""
c = getattr(self.object_list, 'count', None)
if callable(c) and not inspect.isbuiltin(c) and method_has_no_args(c):
return c()
return len(self.object_list)
@cached_property
def num_pages(self):
"""Return the total number of pages."""
if self.count == 0 and not self.allow_empty_first_page:
return 0
hits = max(1, self.count - self.orphans)
return ceil(hits / self.per_page)
@property
def page_range(self):
"""
Return a 1-based range of pages for iterating through within
a template for loop.
"""
return range(1, self.num_pages + 1)
def _check_object_list_is_ordered(self):
"""
Warn if self.object_list is unordered (typically a QuerySet).
"""
ordered = getattr(self.object_list, 'ordered', None)
if ordered is not None and not ordered:
obj_list_repr = (
'{} {}'.format(self.object_list.model, self.object_list.__class__.__name__)
if hasattr(self.object_list, 'model')
else '{!r}'.format(self.object_list)
)
warnings.warn(
'Pagination may yield inconsistent results with an unordered '
'object_list: {}.'.format(obj_list_repr),
UnorderedObjectListWarning,
stacklevel=3
)
def get_elided_page_range(self, number=1, *, on_each_side=3, on_ends=2):
"""
Return a 1-based range of pages with some values elided.
If the page range is larger than a given size, the whole range is not
provided and a compact form is returned instead, e.g. for a paginator
with 50 pages, if page 43 were the current page, the output, with the
default arguments, would be:
1, 2, …, 40, 41, 42, 43, 44, 45, 46, …, 49, 50.
"""
number = self.validate_number(number)
if self.num_pages <= (on_each_side + on_ends) * 2:
yield from self.page_range
return
if number > (1 + on_each_side + on_ends) + 1:
yield from range(1, on_ends + 1)
yield self.ELLIPSIS
yield from range(number - on_each_side, number + 1)
else:
yield from range(1, number + 1)
if number < (self.num_pages - on_each_side - on_ends) - 1:
yield from range(number + 1, number + on_each_side + 1)
yield self.ELLIPSIS
yield from range(self.num_pages - on_ends + 1, self.num_pages + 1)
else:
yield from range(number + 1, self.num_pages + 1)
class Page(collections.abc.Sequence):
def __init__(self, object_list, number, paginator):
self.object_list = object_list
self.number = number
self.paginator = paginator
def __repr__(self):
return '<Page %s of %s>' % (self.number, self.paginator.num_pages)
def __len__(self):
return len(self.object_list)
def __getitem__(self, index):
if not isinstance(index, (int, slice)):
raise TypeError(
'Page indices must be integers or slices, not %s.'
% type(index).__name__
)
# 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.number < self.paginator.num_pages
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):
return self.paginator.validate_number(self.number + 1)
def previous_page_number(self):
return self.paginator.validate_number(self.number - 1)
def start_index(self):
"""
Return the 1-based index of the first object on this page,
relative to total objects in the paginator.
"""
# Special case, return zero if no items.
if self.paginator.count == 0:
return 0
return (self.paginator.per_page * (self.number - 1)) + 1
def end_index(self):
"""
Return the 1-based index of the last object on this page,
relative to total objects found (hits).
"""
# Special case for the last page because there can be orphans.
if self.number == self.paginator.num_pages:
return self.paginator.count
return self.number * self.paginator.per_page