100 lines
3.5 KiB
Python
100 lines
3.5 KiB
Python
class InvalidPage(Exception):
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pass
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class ObjectPaginator(object):
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"""
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This class makes pagination easy. Feed it a QuerySet or list, plus the number
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of objects you want on each page. Then read the hits and pages properties to
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see how many pages it involves. Call get_page with a page number (starting
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at 0) to get back a list of objects for that page.
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Finally, check if a page number has a next/prev page using
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has_next_page(page_number) and has_previous_page(page_number).
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Use orphans to avoid small final pages. For example:
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13 records, num_per_page=10, orphans=2 --> pages==2, len(self.get_page(0))==10
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12 records, num_per_page=10, orphans=2 --> pages==1, len(self.get_page(0))==12
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"""
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def __init__(self, query_set, num_per_page, orphans=0):
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self.query_set = query_set
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self.num_per_page = num_per_page
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self.orphans = orphans
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self._hits = self._pages = None
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self._page_range = None
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def validate_page_number(self, page_number):
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try:
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page_number = int(page_number)
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except ValueError:
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raise InvalidPage
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if page_number < 0 or page_number > self.pages - 1:
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raise InvalidPage
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return page_number
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def get_page(self, page_number):
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page_number = self.validate_page_number(page_number)
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bottom = page_number * self.num_per_page
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top = bottom + self.num_per_page
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if top + self.orphans >= self.hits:
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top = self.hits
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return self.query_set[bottom:top]
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def has_next_page(self, page_number):
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"Does page $page_number have a 'next' page?"
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return page_number < self.pages - 1
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def has_previous_page(self, page_number):
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return page_number > 0
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def first_on_page(self, page_number):
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"""
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Returns the 1-based index of the first object on the given page,
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relative to total objects found (hits).
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"""
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page_number = self.validate_page_number(page_number)
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return (self.num_per_page * page_number) + 1
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def last_on_page(self, page_number):
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"""
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Returns the 1-based index of the last object on the given page,
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relative to total objects found (hits).
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"""
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page_number = self.validate_page_number(page_number)
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page_number += 1 # 1-base
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if page_number == self.pages:
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return self.hits
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return page_number * self.num_per_page
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def _get_hits(self):
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if self._hits is None:
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# Try .count() or fall back to len().
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try:
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self._hits = int(self.query_set.count())
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except (AttributeError, TypeError, ValueError):
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# AttributeError if query_set has no object count.
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# TypeError if query_set.count() required arguments.
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# ValueError if int() fails.
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self._hits = len(self.query_set)
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return self._hits
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def _get_pages(self):
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if self._pages is None:
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hits = (self.hits - 1 - self.orphans)
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if hits < 1:
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hits = 0
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self._pages = hits // self.num_per_page + 1
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return self._pages
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def _get_page_range(self):
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"""
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Returns a 1-based range of pages for iterating through within
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a template for loop.
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"""
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if self._page_range is None:
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self._page_range = range(1, self.pages + 1)
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return self._page_range
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hits = property(_get_hits)
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pages = property(_get_pages)
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page_range = property(_get_page_range)
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