TypeError: list indices must be integers or slices, not str when running Python script

Question

I have run the following Python script to remove duplcates between two json files based on userid:

    import json

    with open("target_user.json", "r", encoding='utf-8') as f1:
        target = json.load(f1)
    with open("source_user.json", "r", encoding='utf-8') as f2:
        source = json.load(f2)
            
    target2 = []
    for item in target:
       if item['userid'] not in [x['userid'] for x in source]:
            target2.append(item)
            
    with open('target_user2.json', 'w', encoding='utf-8') as nf:
        json.dump(target2, nf, indent=4)
        

It generates errors:

    TypeError: list indices must be integers or slices, not str

from this line:

    if item['userid'] not in [x['userid'] for x in source]:

I have tried the following, but it does not fix:

    if dict([item]['userid']) not in [dict[x]['userid'] for x in source]:    

Here is a sample of my json file:

    {
        "567897068": {
            "userid": "567897068",
            "status": "UserStatus.OFFLINE",
            "name": "btb appeal",
            "bot": false,
            "username": "None"
        },
        "5994781619": {
            "userid": "5994781619",
            "status": "UserStatus.OFFLINE",
            "name": "Ahh",
            "bot": false,
            "username": "hourng999"
        },
        "1873973169": {
            "userid": "1873973169",
            "status": "UserStatus.RECENTLY",
            "name": "Chanthy",
            "bot": false,
            "username": "Alis_Thy"
        }
    }

Any help is appreciated.

I have tried the followings advised by John, but it does not:

    import json

    with open("target_user.json", "r", encoding='utf-8') as f1:
        target = json.load(f1)
    with open("source_user.json", "r", encoding='utf-8') as f2:
        source = json.load(f2)
            
    target2 = []
    for item in target.values():
       # print(item) # print scanned results on CMD
        #if item['userid'] not in [x['userid'] for x in source]:
        #if item['userid'] not in [x['userid'] for x in source]:
        if target[item]['userid'] not in [source[x]['userid'] for x in source]:
            target2.append(item)
            
    with open('target_user2.json', 'w', encoding='utf-8') as nf:
        json.dump(target2, nf, indent=4)

Answer 1

I found out that there is an error in the second json file, that is why there is error mentioned. My original codes are working well. the correct format of that second file is:

    [
           {
                "userid": "567897068",
                "status": "UserStatus.OFFLINE",
                "name": "btb appeal",
                "bot": false,
                "username": "None"
            },
            {
                "userid": "5994781619",
                "status": "UserStatus.OFFLINE",
                "name": "Ahh",
                "bot": false,
                "username": "hourng999"
            },
            {
                "userid": "1873973169",
                "status": "UserStatus.RECENTLY",
                "name": "Chanthy",
                "bot": false,
                "username": "Alis_Thy"
            }
    ]

It is different from the first file; that was why the original codes dont work - both files must have the same format. Thanks