Check if value already exists within list of dictionaries?

Question

I\'ve got a Python list of dictionaries, as follows:

a = [
    {\'main_color\': \'red\', \'second_color\':\'blue\'},
    {\'main_color\': \'yellow\', \'secon         


        

Answer 1

Here's one way to do it:

if not any(d['main_color'] == 'red' for d in a):
    # does not exist

The part in parentheses is a generator expression that returns True for each dictionary that has the key-value pair you are looking for, otherwise False.

---

If the key could also be missing the above code can give you a KeyError. You can fix this by using get and providing a default value. If you don't provide a default value, None is returned.

if not any(d.get('main_color', default_value) == 'red' for d in a):
    # does not exist