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

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)