Ticket #2575: better_paginator.patch

File better_paginator.patch, 5.2 KB (added by SmileyChris, 9 years ago)
  • core/paginator.py

     
    1 from math import ceil
    2 
    31class InvalidPage(Exception):
    42    pass
    53
    64class ObjectPaginator(object):
    75    """
    8     This class makes pagination easy. Feed it a QuerySet, plus the number of
    9     objects you want on each page. Then read the hits and pages properties to
     6    This class makes pagination easy. Feed it a QuerySet or list, plus the number
     7    of objects you want on each page. Then read the hits and pages properties to
    108    see how many pages it involves. Call get_page with a page number (starting
    119    at 0) to get back a list of objects for that page.
    1210
    1311    Finally, check if a page number has a next/prev page using
    1412    has_next_page(page_number) and has_previous_page(page_number).
     13   
     14    Use orphan to avoid small final pages. For example:
     15    13 records, num_per_page=10, orphan=2 --> pages==2, len(self.get_page(0))==10
     16    12 records, num_per_page=10, orphan=2 --> pages==1, len(self.get_page(0))==12
    1517    """
    16     def __init__(self, query_set, num_per_page):
     18    def __init__(self, query_set, num_per_page, orphan=0):
    1719        self.query_set = query_set
    1820        self.num_per_page = num_per_page
    19         self._hits, self._pages = None, None
    20         self._has_next = {} # Caches page_number -> has_next_boolean
     21        self.orphan = orphan
     22        self._hits = self._pages = None
    2123
    22     def get_page(self, page_number):
     24    def validate_page_number(self, page_number):
    2325        try:
    2426            page_number = int(page_number)
    2527        except ValueError:
    2628            raise InvalidPage
    27         if page_number < 0:
     29        if page_number < 0 or page_number > self.pages - 1:
    2830            raise InvalidPage
     31        return page_number
    2932
    30         # Retrieve one extra record, and check for the existence of that extra
    31         # record to determine whether there's a next page.
    32         limit = self.num_per_page + 1
    33         offset = page_number * self.num_per_page
     33    def get_page(self, page_number):
     34        page_number = self.validate_page_number(page_number)
     35        bottom = page_number * self.num_per_page
     36        top = bottom + self.num_per_page
     37        if top + self.orphan >= self.hits:
     38            top = self.hits
     39        return self.query_set[bottom:top]
    3440
    35         object_list = list(self.query_set[offset:offset+limit])
    36 
    37         if not object_list:
    38             raise InvalidPage
    39 
    40         self._has_next[page_number] = (len(object_list) > self.num_per_page)
    41         return object_list[:self.num_per_page]
    42 
    4341    def has_next_page(self, page_number):
    4442        "Does page $page_number have a 'next' page?"
    45         if not self._has_next.has_key(page_number):
    46             if self._pages is None:
    47                 offset = (page_number + 1) * self.num_per_page
    48                 self._has_next[page_number] = len(self.query_set[offset:offset+1]) > 0
    49             else:
    50                 self._has_next[page_number] = page_number < (self.pages - 1)
    51         return self._has_next[page_number]
     43        return page_number < self.pages - 1
    5244
    5345    def has_previous_page(self, page_number):
    5446        return page_number > 0
     
    5850        Returns the 1-based index of the first object on the given page,
    5951        relative to total objects found (hits).
    6052        """
    61         if page_number == 0:
    62             return 1
     53        page_number = self.validate_page_number(page_number)
    6354        return (self.num_per_page * page_number) + 1
    6455
    6556    def last_on_page(self, page_number):
     
    6758        Returns the 1-based index of the last object on the given page,
    6859        relative to total objects found (hits).
    6960        """
    70         if page_number == 0 and self.num_per_page >= self._hits:
    71             return self._hits
    72         elif page_number == (self._pages - 1) and (page_number + 1) * self.num_per_page > self._hits:
    73             return self._hits
    74         return (page_number + 1) * self.num_per_page
     61        page_number = self.validate_page_number(page_number)
     62        page_number += 1   # 1-base
     63        if page_number == self.pages:
     64            return self.hits
     65        return page_number * self.num_per_page
    7566
    7667    def _get_hits(self):
    7768        if self._hits is None:
    78             self._hits = self.query_set.count()
     69            # Try .count() or fall back to len().
     70            try:
     71                self._hits = int(self.query_set.count())
     72            except AttributeEror, TypeError, ValueError:
     73                # AttributeError if query_set has no object count.
     74                # TypeError if query_set.count() required arguments.
     75                # ValueError if int() fails.
     76                self._hits = len(self.query_set)
     77            else:
    7978        return self._hits
    8079
    8180    def _get_pages(self):
    8281        if self._pages is None:
    83             self._pages = int(ceil(self.hits / float(self.num_per_page)))
     82            hits = (self.hits - 1 - self.orphan)
     83            if hits < 1:
     84                hits = 0
     85            self._pages = hits // self.num_per_page + 1
    8486        return self._pages
    8587
    8688    hits = property(_get_hits)
    87     pages = property(_get_pages)
     89    pages = property(_get_pages)
     90 No newline at end of file
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