with open(path_to_js) as _f:
    data_a = json.load(_f)
    structure = data_a['structure']
    data_a['structure']['alarm_status'].remove(0)
    data_a['structure']['alarm_status'].append(1)

{
  "structure": [
        {
            "host": "relife.pro",
            "username": "bot",
            "private_key": "./src_1/db/bot.key",
            "alarm_status":[0]
        }
    ]
}

data_a['structure']['alarm_status'].remove(0)
TypeError: list indices must be integers or slices, not str

with open(path_to_js) as _f:
    data_a = json.load(_f)
    structure = data_a['structure']
    data_a['structure']['alarm_status'].remove(0)
    data_a['structure']['alarm_status'].append(1)

{
  "structure": [
        {
            "host": "relife.pro",
            "username": "bot",
            "private_key": "./src_1/db/bot.key",
            "alarm_status":[0]
        }
    ]
}

data_a['structure']['alarm_status'].remove(0)
TypeError: list indices must be integers or slices, not str