How to categorize list of dictionaries based on the value of a key in python efficiently?

Question

I have a list of dictionaries in python which I want to categorized them based on the value of a key which exists in all dictionaries and process each category separately. I don't know what are the values, I just know that there exists a special key. Here's the list:

dictList = [
            {'name': 'name1', 'type': 'type1', 'id': '14464'}, 
            {'name': 'name2', 'type': 'type1', 'id': '26464'},
            {'name': 'name3', 'type': 'type3', 'id': '36464'},
            {'name': 'name4', 'type': 'type5', 'id': '43464'},
            {'name': 'name5', 'type': 'type2', 'id': '68885'}
            ]

This is the code I currently use:

while len(dictList):
    category = [l for l in dictList if l['type'] == dictList[0]['type']]
    processingMethod(category)
    for item in category:
        dictList.remove(item)

This iteration on the above list will give me following result:

Iteration 1:
            category = [
                        {'name': 'name1', 'type': 'type1', 'id': '14464'}, 
                        {'name': 'name2', 'type': 'type1', 'id': '26464'},
                        ]

Iteration 2:
            category = [
                        {'name': 'name3', 'type': 'type3', 'id': '36464'}
                        ]

Iteration 3:
            category = [
                        {'name': 'name4', 'type': 'type5', 'id': '43464'}
                        ]

Iteration 4:
            category = [
                        {'name': 'name5', 'type': 'type2', 'id': '68885'}
                        ]

Each time, I get a category, process it and finally remove processed items to iterate over remaining items, until there is no remaining item. Any idea to make it better?

Answer 1

Your code can be rewritten using itertools.groupby

for _, category in itertools.groupby(dictList, key=lambda item:item['type']):
    processingMethod(list(category))

Or if processingMethod can process iterable,

for _, category in itertools.groupby(dictList, key=lambda item:item['type']):
    processingMethod(category)