Python: 'NoneType' object is not subscriptable

Question

Asking for some help on this one.

def home(request):
    client = pymongo.MongoClient(settings.MONGO_SERVER)
    main_db = client[settings.MONGO_DATABASE]
    get_main_config = main_db.configurations.find_one({"name": "main_config"})

    return render(request, 'dashboard/home.html', {"data": get_main_config["homepage_urls"]})

Traceback (most recent call last):
render(request, 'dashboard/home.html', {"data": get_main_config["homepage_urls"]})
TypeError: 'NoneType' object is not subscriptable

Why the error occured on that line? Thank you.

Sounds like get_main_config is None. Are you sure that main_db.configurations_find_one doesn't ever return None? — Samwise
– Samwise, Commented Jul 26, 2022 at 2:37

Calvin · Accepted Answer · 2022-07-26 02:39:49Z

1

The error shows up when you use operator [] on a variable whose value is None. So it can only be get_main_config. Just print the variable to check.

answered Jul 26, 2022 at 2:39

Calvin

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Red · Accepted Answer · 2022-07-26 12:10:30Z

0

It means that get_main_config is of type None and None is not a subscriptable type. For an object to be subscriptable in Python it must support indexing (lists, tuples, strings etc. are subscriptable). Here, since get_main_config is None (which does not support indexing) and you are trying to access the key 'homepage_urls' from it you end up with the error you got.

The find_one method you are using is designed to find a single document matching your query or return None if it could not find any. (https://pymongo.readthedocs.io/en/stable/tutorial.html#getting-a-single-document-with-find-one)

So, you may want to make sure that a document matching the query {'name': 'main_config'} actually exists in your database.

edited Jul 26, 2022 at 12:10

answered Jul 26, 2022 at 3:54

Red

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