pagination frontend with Django

custom_pagination.py

#
# File templatetags/custom_pagination.py
#

from django import template

register = template.Library()


@register.simple_tag
def add_param_into_url(url: str, key: str, value: str):
    if key in url:
        try:
            idx = url.index('?%s=' % key)
        except ValueError:
            try:
                idx = url.index('&%s=' % key)
            except ValueError:
                idx = None
        if idx:
            val_idx = url.index('=', idx) + 1
            try:
                end_val_idx = url.index('&', val_idx)
                old_value = url[val_idx: end_val_idx]
            except ValueError:
                old_value = url[val_idx:]
            url = url.replace('{}={}'.format(key, old_value), '{}={}'.format(key, value))
    else:
        if '?' in url:
            if url.endswith('?'):
                url += '{key}={value}'.format(**locals())
            else:
                url += '&{key}={value}'.format(**locals())
        else:
            url += '?{key}={value}'.format(**locals())

    return url


@register.filter
def pagination_range(obj, current=1, limit=5):
    left = (limit // 2) + 1
    right = limit // 2
    total = len(obj)

    if limit % 2 == 0:
        right -= 1

    _range = []

    if current < left:
        _range = list(obj[:limit])
    if current > total - right:
        _range = list(obj[total-limit:])

    idx_from = current - left
    idx_to = current + right
    if not _range:
        _range = list(obj[idx_from:idx_to])

    first_page = _range[0]
    if first_page > 1:
        _range.insert(0, 1)
        if first_page - 1 > 1:
            _range.insert(1, -1)
    last_page = _range[len(_range) - 1]
    num_pages = len(obj)
    if last_page < num_pages:
        if num_pages - last_page > 1:
            _range.append(-1)
        _range.append(num_pages)

    return _range

pagination_block.html

{% load custom_pagination %}


<ul class="pagination">
    {% if page_obj.has_previous %}
        <li class="page-item">
            <a class="page-link" href="{% add_param_into_url request.get_full_path 'page' page_obj.previous_page_number %}">
                {% trans "Previous" %}
            </a>
        </li>
    {% endif %}

    {% for page in paginator.page_range|pagination_range:page_obj.number %}
        {% if page == -1 %}
            <li class="page-item"><a class="page-link" disabled>...</a></li>
        {% else %}
            <li class="page-item {% if page == page_obj.number %}active{% endif %}">
                <a class="page-link" href="{% add_param_into_url request.get_full_path 'page' page %}">{{ page }}</a>
            </li>
        {% endif %}
    {% endfor %}

    {% if page_obj.has_next %}
        <li class="page-item">
            <a class="page-link" href="{% add_param_into_url request.get_full_path 'page' page_obj.next_page_number %}">
                {% trans "Next" %}
            </a>
        </li>
    {% endif %}
</ul>