from django import template

register = template.Library()

@register.simple_tag
def my_url(value, field_name, urlencode=None):
    url = '?{}={}'.format(field_name,value)


    if urlencode:
        querystring = urlencode.split('&')
        filtered_querystring = filter(lambda p: p.split('=')[0]!=field_name, querystring)
        encoded_querystring = '&'.join(filtered_querystring)
        url = '{}&{}'.format(url,encoded_querystring)


    return url