Google-like pagination algorithm

paging.py

#!/usr/bin/env python3

# heavily inspired by https://jasonwatmore.com/post/2016/01/31/angularjs-pagination-example-with-logic-like-google

import math

def paginate(curr, itemsPerPage, numItems, numPagesToShowAtOnce):
    # ceil here to make sure we don't miss anything
    half = math.ceil(numPagesToShowAtOnce / 2)
    numPages = math.ceil(numItems / itemsPerPage)

    if numPages <= numPagesToShowAtOnce:
        # show all pages
        lo = 1
        hi = numPages

    else:
        if curr <= half:
            # lower bound
            lo = 1
            hi = numPagesToShowAtOnce

        elif curr + half >= numPages:
            # higher bound
            lo = numPages - numPagesToShowAtOnce
            hi = numPages

        else:
            # middle
            lo = curr - half
            hi = curr + half

        # ellipsis check lower bound
        if lo > 1:
            print(" 1 ", end="")
        if lo > 2:
            print("...", end="")

        # output the range, highlighting curr with []
        for i in range(lo, hi + 1):
            if i == curr:
                print("[{}]".format(i), end="")
            else:
                print(" {} ".format(i), end="")

        # ellipsis check upper bound
        if hi < numPages - 1:
            print("...", end="")
        if hi < numPages:
            print(" {} ".format(numPages), end="")


for curr in range(1, 25 + 1):
    paginate(curr=curr, itemsPerPage=10, numItems=250, numPagesToShowAtOnce=10)
    print()

# note that curr is always centered unless it's close to the 
# outputs the following:
"""
[1] 2  3  4  5  6  7  8  9  10 ... 25 
 1 [2] 3  4  5  6  7  8  9  10 ... 25 
 1  2 [3] 4  5  6  7  8  9  10 ... 25 
 1  2  3 [4] 5  6  7  8  9  10 ... 25 
 1  2  3  4 [5] 6  7  8  9  10 ... 25 
 1  2  3  4  5 [6] 7  8  9  10  11 ... 25 
 1  2  3  4  5  6 [7] 8  9  10  11  12 ... 25 
 1 ... 3  4  5  6  7 [8] 9  10  11  12  13 ... 25 
 1 ... 4  5  6  7  8 [9] 10  11  12  13  14 ... 25 
 1 ... 5  6  7  8  9 [10] 11  12  13  14  15 ... 25 
 1 ... 6  7  8  9  10 [11] 12  13  14  15  16 ... 25 
 1 ... 7  8  9  10  11 [12] 13  14  15  16  17 ... 25 
 1 ... 8  9  10  11  12 [13] 14  15  16  17  18 ... 25 
 1 ... 9  10  11  12  13 [14] 15  16  17  18  19 ... 25 
 1 ... 10  11  12  13  14 [15] 16  17  18  19  20 ... 25 
 1 ... 11  12  13  14  15 [16] 17  18  19  20  21 ... 25 
 1 ... 12  13  14  15  16 [17] 18  19  20  21  22 ... 25 
 1 ... 13  14  15  16  17 [18] 19  20  21  22  23 ... 25 
 1 ... 14  15  16  17  18 [19] 20  21  22  23  24  25 
 1 ... 15  16  17  18  19 [20] 21  22  23  24  25 
 1 ... 15  16  17  18  19  20 [21] 22  23  24  25 
 1 ... 15  16  17  18  19  20  21 [22] 23  24  25 
 1 ... 15  16  17  18  19  20  21  22 [23] 24  25 
 1 ... 15  16  17  18  19  20  21  22  23 [24] 25 
 1 ... 15  16  17  18  19  20  21  22  23  24 [25]
"""