Python matching keys in list of dicitonaries

I have the following list of dictionaries, with sub dictionaries data:

data2 = [
    {"dep": None},
    {"dep": {
            "eid": "b3ca7ddc-0d0b-4932-816b-e74040a770ec",
            "nid": "fae15b05-e869-4403-ae80-6e8892a9dbde",
        }
    },
    {"dep": None},
    {"dep": {
            "eid": "c3bcaef7-e3b0-40b6-8ad6-cbdb35cd18ed",
            "nid": "6a79c93f-286c-4133-b620-66d35389480f",
        }
    },
]

And I have a match key:

match_key = "b3ca7ddc-0d0b-4932-816b-e74040a770ec"

And I want to see if any sub dictionaries of each "dep" key in data2 have an eid that matches my match_key. I’m trying the following, but I get a TypeError: string indices must be integers – where am I going wrong?

My Code

matches = [
            d["eid"]
            for item in data2
            if item["dep"]
            for d in item["dep"]
            if d["eid"] == match_key
        ]

So matches should return:

["b3ca7ddc-0d0b-4932-816b-e74040a770ec"]

Meaning it found this id in data2.

>Solution :

When you iterate over a dictionary, each iteration gives you a key from the dictionary.

So d["eid"] is actually "eid"["eid"], which is an invalid expression. That’s why Python raises the following exception:

TypeError: string indices must be integers

Also, the expression d["eid"] assumes that every d contains the eid key. If it doesn’t, Python will raise a KeyError.

If you don’t know for sure that "eid" is a valid key in the dictionary, prefer using the .get method instead.

matches = [
    v
    for item in data2
    if item.get("dep")  # Is there a key called dep, and it has a non-falsy value in it
    for k, v in item["dep"].items()  # Iterate over the dictionary items
    if k == "eid" and v == match_key
]

You can do even better by directly accessing the value of eid key:

matches = [
    d["dep"]["eid"]
    for d in data2
    if d.get("dep") and d["dep"].get("eid") == match_key
]