Get Values of Particular Key in List of Dictionaries - Python

We are given a list of dictionaries and a particular key. Our task is to retrieve the values associated with that key from each dictionary in the list. If the key doesn't exist in a dictionary, it should be ignored. For example, if we have the following list of dictionaries and we want to extract the values for the key 'aryan': li = [{'aryan': 10, 'harsh': 20}, {'aryan': 30, 'kunal': 40}, {'harsh': 50}] then the output will be [10, 30].

Using List Comprehension

We use List comprehension to iterate over the list of dictionaries and retrieve the values associated with the particular key. If the key exists in the dictionary then the value will be appended to the result list.

[10, 30]

Explanation:

• [d.get(k) for d in li if k in d] loops over each dictionary in the list and checks if the key k exists, and if so then retrieves the value using get(k).
• d.get(k) retrieves the value associated with the key k if it exists otherwise it returns None.

Using map() and lambda

We can use map() function to extract the key values directly after filtering the dictionaries that have the key using filter() function.

[10, 30]

Explanation:

• filter(lambda d: k in d, li) filters the dictionaries to include only those that contain the key k.
• map(lambda d: d.get(k), ...) maps the remaining dictionaries to their corresponding values using get(k).

Using a For Loop

In this method we use a for loop to manually iterate over the list of dictionaries and check for the key, if present then collect the values and store in result.

[10, 30]

Explanation:

• for d in li: loops over each dictionary in the list and if k in d: checks if the dictionary contains the key k.
• res.append(d[k]) is used to add the value for the key k to the result list.