How to find a number +1 to the largest in a list OR fill any numerical gaps

I am interacting with an API. I am using a GET (requests) to get the data I need. The response looks like this:

[{'AG': '**********************************',
  'AB': '**********************************',
  'AC': '**********************************',
  'AD': '**********************************',
  'AE': '**********************************',
  'description': 'TEST1',
  'id': 1,
  'code': '**********************************',
  'definer': '**********************************',
  'paraJ': 1,
  'G1': '****',
  'B2': '****',
  'A3': '****',
  'F4': '****',
  'C5': '****'},
 {'AG': '**********************************',
  'AB': '**********************************',
  'AC': '**********************************',
  'AD': '**********************************',
  'AE': '**********************************',
  'description': 'TEST2',
  'id': 2,
  'code': '**********************************',
  'definer': '**********************************',
  'paraJ': 22,
  'G1': '****',
  'B2': '****',
  'A3': '****',
  'F4': '****',
  'C5': '****'}]

I am then parsing out just the id. Using this:
param_ids = [element['id'] for element in param_current_ids_dict]

So I'm left with:

[1, 2]

My question is this: How can I check for the next largest number to use? Ideally, I'd want to send a POST to the API with the id of 3, as my next action, since that is the next available digit after 2. Also it would be nice if it 'filled' any gaps. Say the response was:
[1, 3]
'2' would be fine in this instance.

To find the next largest number that is not already in the list, you can sort the list of ids and iterate over them, comparing each element to its index plus 1 (since you want the next number). When you find an element that is greater than its index plus 1, return that index plus 1 as the next available id.

param_current_ids_dict = [{'AG': '**********************************',
  'AB': '**********************************',
  'AC': '**********************************',
  'AD': '**********************************',
  'AE': '**********************************',
  'description': 'TEST1',
  'id': 1,
  'code': '**********************************',
  'definer': '**********************************',
  'paraJ': 1,
  'G1': '****',
  'B2': '****',
  'A3': '****',
  'F4': '****',
  'C5': '****'},
 {'AG': '**********************************',
  'AB': '**********************************',
  'AC': '**********************************',
  'AD': '**********************************',
  'AE': '**********************************',
  'description': 'TEST2',
  'id': 3,
  'code': '**********************************',
  'definer': '**********************************',
  'paraJ': 22,
  'G1': '****',
  'B2': '****',
  'A3': '****',
  'F4': '****',
  'C5': '****'}]


param_ids = [element['id'] for element in param_current_ids_dict]


def next_available_id(ids):
    sorted_ids = sorted(ids)
    for i, id in enumerate(sorted_ids):
        if id > i + 1:
            return i + 1
    return len(ids) + 1

next_id = next_available_id(param_ids)

print(next_id) # should print 2 in this case

Easy and effective python script:

input_list = [1, 3]


def check_id(input_list, fill_all_gaps=False):
    available_numbers = [i+1 for i in range(100)]
    for nr in input_list:
        available_numbers.remove(nr)

    if not fill_all_gaps:
        return available_numbers[0] 
    else:
        return available_numbers[:max(input_list) - len(input_list)]

If you want just the next acceptable id you can use:

print(check_id(input_list))

2 # number as integer

If you want all available id's:

input_list = [2, 5]

print(check_id(input_list, fill_all_gaps=True))

[1, 3, 4] # number/s as list