autovivification – Tarik Billa

What’s the best way to initialize a dict of dicts in Python? [duplicate]

January 22, 2023 by Tarik

If the amount of nesting you need is fixed, collections.defaultdict is wonderful. e.g. nesting two deep: myhash = collections.defaultdict(dict) myhash[1][2] = 3 myhash[1][3] = 13 myhash[2][4] = 9 If you want to go another level of nesting, you’ll need to do something like: myhash = collections.defaultdict(lambda : collections.defaultdict(dict)) myhash[1][2][3] = 4 myhash[1][3][3] = 5 myhash[1][2][‘test’] … Read more

What is the best way to implement nested dictionaries?

October 11, 2022 by Tarik

What is the best way to implement nested dictionaries in Python? This is a bad idea, don’t do it. Instead, use a regular dictionary and use dict.setdefault where apropos, so when keys are missing under normal usage you get the expected KeyError. If you insist on getting this behavior, here’s how to shoot yourself in … Read more