Ticket #2093: better_paginator.patch

File better_paginator.patch, 5.0 KB (added by Chris Beaven, 18 years ago)

  • paginator.py

     
    1 from copy import copy
    2 from math import ceil
    3 
    41class InvalidPage(Exception):
    52    pass
    63
    74class ObjectPaginator:
    85    """
    9     This class makes pagination easy. Feed it a QuerySet, plus the number of
    10     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
    118    see how many pages it involves. Call get_page with a page number (starting
    129    at 0) to get back a list of objects for that page.
    1310
    1411    Finally, check if a page number has a next/prev page using
    1512    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
    1617    """
    17     def __init__(self, query_set, num_per_page):
     18    def __init__(self, query_set, num_per_page, orphan=0):
    1819        self.query_set = query_set
    1920        self.num_per_page = num_per_page
    20         self._hits, self._pages = None, None
    21         self._has_next = {} # Caches page_number -> has_next_boolean
     21        self.orphan = orphan
     22        self._hits = self._pages = None
    2223
    23     def get_page(self, page_number):
     24    def validate_page_number(self, page_number):
    2425        try:
    2526            page_number = int(page_number)
    2627        except ValueError:
    2728            raise InvalidPage
    28         if page_number < 0:
     29        if page_number < 0 or page_number > self.pages - 1:
    2930            raise InvalidPage
     31        return page_number
    3032
    31         # Retrieve one extra record, and check for the existence of that extra
    32         # record to determine whether there's a next page.
    33         limit = self.num_per_page + 1
    34         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]
    3540
    36         object_list = list(self.query_set[offset:offset+limit])
    37 
    38         if not object_list:
    39             raise InvalidPage
    40 
    41         self._has_next[page_number] = (len(object_list) > self.num_per_page)
    42         return object_list[:self.num_per_page]
    43 
    4441    def has_next_page(self, page_number):
    4542        "Does page $page_number have a 'next' page?"
    46         if not self._has_next.has_key(page_number):
    47             if self._pages is None:
    48                 offset = (page_number + 1) * self.num_per_page
    49                 self._has_next[page_number] = len(self.query_set[offset:offset+1]) > 0
    50             else:
    51                 self._has_next[page_number] = page_number < (self.pages - 1)
    52         return self._has_next[page_number]
     43        return page_number < self.pages - 1
    5344
    5445    def has_previous_page(self, page_number):
    5546        return page_number > 0
    … …  
    5950        Returns the 1-based index of the first object on the given page,
    6051        relative to total objects found (hits).
    6152        """
    62         if page_number == 0:
    63             return 1
     53        page_number = self.validate_page_number(page_number)
    6454        return (self.num_per_page * page_number) + 1
    6555
    6656    def last_on_page(self, page_number):
    … …  
    6858        Returns the 1-based index of the last object on the given page,
    6959        relative to total objects found (hits).
    7060        """
    71         if page_number == 0 and self.num_per_page >= self._hits:
    72             return self._hits
    73         elif page_number == (self._pages - 1) and (page_number + 1) * self.num_per_page > self._hits:
    74             return self._hits
    75         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
    7666
    7767    def _get_hits(self):
    7868        if self._hits is None:
    79             self._hits = self.query_set.count()
     69            # If query_set is a list or tuple, use len(self.query_set) otherwise assume
     70            # that it is a QuerySet and use .count().
     71            if isinstance(self.query_set, list) or isinstance(self.query_set, tuple):
     72                self._hits = len(self.query_set)
     73            else:
     74                self._hits = self.query_set.count()
    8075        return self._hits
    8176
    8277    def _get_pages(self):
    8378        if self._pages is None:
    84             self._pages = int(ceil(self.hits / float(self.num_per_page)))
     79            hits = (self.hits - 1 - self.orphan)
     80            if hits < 1:
     81                hits = 0
     82            self._pages = hits // self.num_per_page + 1
    8583        return self._pages
    8684
    8785    hits = property(_get_hits)
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