paginator.py

import math
from django.core.paginator import Paginator, Page

"""
Pagination classes for windowed/ranged pagination
"""

class WindowPaginator(Paginator):
    
    def page(self, number, window=None):
        
        """
        Returns a Page object for the given 1-based page number.
        This is a copy of Paginator.page, but returning a WindowPage 
        instance instead of a Page one
        """
        
        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 WindowPage(self.object_list[bottom:top], number, self, window=window)

class WindowPage(Page):
    def __init__(self, object_list, number, paginator, window=None):
        
        """
        WindowPage object constructor
        
        `window`
        A number indicating how many page links you want to display in between the first and last pages.
        Example: a value of '5' with a total of 30 pages, on page 14 would yield a page range of:
        [1, None, 12, 13, 14, 15, 16, None, 30]
        """
        
        super(WindowPage, self).__init__(object_list, number, paginator)
        self.window = window
    
    def _get_page_range(self):
        if self.window and self.window + 2 < self.paginator.num_pages: # If a window is set, and that window plus the first and last pages is less than the total...
            
            # Calculate lower and higher window limits
            
            page_max = self.paginator.num_pages
            offset = int(math.floor(float(self.window - 1) / 2))
            lower = self.number - offset
            higher = self.number + (self.window - offset)
            
            if lower <= 2:
                lower = 2
                higher = 2 + self.window
            elif higher >= page_max:
                higher = page_max
                lower = higher - self.window
            
            # Build pages list
            
            pages = [1]
            
            if lower > 2:
                pages.append(None)
            
            pages.extend(range(lower, higher))
            
            if higher < page_max - 1:
                pages.append(None)
            
            pages.append(page_max)
            
            return pages
        else:
            return self.paginator._get_page_range()
    
    page_range = property(_get_page_range)