[FIXED] How to count occurrences of key in list of dictionaries

Issue

I know this is a frequently asked question, however I do not have access to the Counter module as I'm using v2.6 of Python. I want to count the number of time a specific key appears in a list of dictionaries.

If my dictionary looks like this:

data = [{'a':1, 'b':1}, {'a':1, 'c':1}, {'b':1, 'c':1}, {'a':1, 'c':1}, {'a':1, 'd':1}]

How would I find out how many times "a" appears? I've tried using len, but that only returns the number of values for one key.

len(data['a'])

Solution

You can use list comprehension.

data = [{'a':1, 'b':1}, {'a':1, 'c':1}, {'b':1, 'c':1}, {'a':1, 'c':1}, {'a':1, 'd':1}]
sum([1 for d in data if 'a' in d])

Explanation: First take the dictionary object from list data, check if key 'a' is present in the dictionary or not, if present, add 1 to the list. Then sum the new list.

Answered By - shaeed