Inserting items in a list with python while looping

Question

I’am trying to change the following code to get the following return :

"1 2 3 … 31 32 33 34 35 36 37 … 63 64 65"

def createFooter2(current_page, total_pages, boundaries, around) -> str:
    footer = []
    page = 1
    #Append lower boundaries
    while page <= boundaries:
        footer.append(page)
        page += 1
    #Append current page and arround
    page = current_page - around
    while page <= current_page + around:
        footer.append(page)
        page += 1
    #Append upper boundaries
    page = total_pages - boundaries + 1
    while page <= total_pages:
        footer.append(page)
        page += 1
    #Add Ellipsis if necessary
    for i in range(len(footer)):
        if i > 0 and footer[i] - footer[i - 1] > 1:
            footer.insert(i, "...")
    result = ' '.join(str(page) for page in result)
    print(result)
    return result

createFooter2(34, 65, 3, 3)

I want to insert an "…" between the pages if the next page is not directly next to it. However Iam having trouble inserting into the list.

How should I change the code to make it work ?

Asked By: Simao

||

Source

Answer 1

As I commented, I first log all discontinuity indexes, then insert ‘…’ from higher to lower (since modifying an iterable you’re looping through will cause problems otherwise):

a = list(range(50))
a.remove(6)
a.remove(23)
a.remove(45)

indexes = []
for i in range(1,len(a)):
    if a[i] != a[i-1]+1:
        indexes.append(i)

for i in indexes[::-1]:
    a.insert(i,'...')

a
# [0, 1, 2, 3, 4, 5, '...', 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, '...', 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, '...', 46, 47, 48, 49]

Answered By: Swifty

Answer 2

This produces a sorted list of page numbers in the first step and then adds "..." to gaps between the numbers. Nothing special, but it should produce a sane output even if there are not 3 intervals (i.e. 2 gaps between them), but some of the intervals overlap (1 gap, or no gap at all).

def createFooter2(current_page, total_pages, boundaries, around) -> str:
    intervals = [ 
            (1, boundaries),
            (current_page - around, current_page + around),
            (total_pages - boundaries + 1, total_pages)
            ]   
    pages = set()
    for start, stop in intervals:
        pages.update(range(max(1, start), min(stop, total_pages) + 1))

    footer = []
    last = 0 
    for i in sorted(pages):
        if i != last + 1:
            footer.append('...')
        footer.append(str(i))
        last = i 
    print(" ".join(footer))

Answered By: VPfB

Inserting items in a list with python while looping

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