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Pythonic way to aggregate or group elements in a list using dict.get and dict.setdefault

Micheal Ojemoron on February 22, 2020

Using dict.get How often have you aggregated an item by its group like this: ar= [1,1,3,1,2,1,3,3,3,3] pairs = {} for i in ar: if...

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Pacharapol Withayasakpunt • Feb 22 '20

This is just too magical, and hard to understand.

items_by_type = {}
for item in items:
    items_by_type.setdefault(item.type, list()).append(item)

A less magical version is defaultdict (from collections)

items_by_type = defaultdict(list)
for item in items:
    items_by_type[item.type].append(item)

Waylon Walker • Feb 22 '20 • Edited

Diddo the swap from

for i in range(len(items)):
   ...

for item in items:
   ...

Micheal Ojemoron • Feb 22 '20

you are absolutely right, I have updated the code. Thanks

Micheal Ojemoron • Feb 22 '20 • Edited

You are right😁, fortunately there are several ways to do things in Python. I am more concerned about using dictionary methods. Thank you

Waylon Walker • Feb 22 '20

Good walk of the different dictionary methods.

Micheal Ojemoron • Feb 22 '20

Thanks

Waylon Walker • Feb 22 '20

I love the Counter object. I've had a rest API getting bogged down with pandas trying to count something and it took a few seconds for each response. Counter was just a few ms.

Micheal Ojemoron • Feb 22 '20

Great!

Blessed J. Eikhiena • Feb 22 '20

Great!

Micheal Ojemoron • Feb 22 '20

Thanks