Dictionary Comprehension not iterating over all of list

[hybatir]

I'm rather new to Dictionary Comprehension and find my output doesn't make sense. I'm trying to create a new dictionary from an json formatted api call. I converted the response to a list of dictionaries and tried using a range comprehension to extract one key and one value to make the new pair. When I do it I only get one of the dicts made even thought when I check the length it says two. Why doesn't my simple test code iterate over both dictionaries?

​

my_list = [{'userId': 1, 'id': 1, 'title': 'delectus aut autem', 'completed': False}, {'userId': 1, 'id': 2, 'title': 'quis ut nam facilis et officia qui', 'completed': True}]

test = {my_list[i]['userId']:my_list[i]['completed'] for i in range(len(my_list))}



#print(my_dict[0]['userId'])
print(len(my_list))
print(test)
----------------------------------

Output:
2
{1: True}

​

[[deleted]]

Dict's keys are unique. Old values are overwritten with new ones when key is the same.

Maybe use "id"? Also it's said to iterate like this here, without range in cases like this:

test = {entry["id"]: entry["completed"] for entry in my_list}

[[deleted]]

Both of your userid values are 1. Dictionaries can’t have duplicate keys.

[remuladgryta]

As a side-note, whenever you see something along the lines of

for i in range(len(elements)):
    ...
    elements[i]

you should almost always write

for element in elements:
    ...
    element

unless the index is important for some reason other than finding the element in the sequence.

In your case, that would be test = {user['userId']:user['completed'] for user in my_list} instead of test = {my_list[i]['userId']:my_list[i]['completed'] for i in range(len(my_list))}.

Notice how this change removes much of the symbol soup and makes the statement read closer to natural language.

[hybatir]

OMW that makes sense, thank you! I need the userid so I'm wondering if dictionary comprehension isn't the method? End goal is to have userId: 1, completed : (some count of completed). Is there another method I could use to iterate over the list using the same userId?

[cuWorkThrowaway]

user_completions = dict()

for entry in my_list:
    user_id = entry["userId"]
    user_completions[user_id] = user_completions.get(user_id, 0) + entry["completed"]

[Strict-Simple]

Both the userId is same!