Python initialize empty dictionary with default values type

Question

I want to use a dictionary with string as key and set() as values.

How do I initialize an empty dictionary with a specific type as values?

I need it because I don't want to check everytime if the key is already in the dictionary and put an if to create the set instead of just using .add()

is it possible?

Does this answer your question? Dictionaries and default values — AMC
– AMC, Commented Mar 23, 2020 at 21:39

Seleme · Accepted Answer · 2020-03-23 18:41:42Z

3

Use defaultdict

from collections import defaultdict
mydict = defaultdict(set)
mydict["key"].add(5)

answered Mar 23, 2020 at 18:41

Seleme

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1 Comment

Egret Over a year ago

Is it also possible to use just dict? i.e. mydict = dict(set)

Utsav Chokshi · Accepted Answer · 2020-03-24 17:59:14Z

0

You can also use setdefault() function on standard python dict to initialize keys not present.

setdefault() :

returns default value passed if key is not present.
returns None if key is not present and no default value passed
returns value of key if key is present.

    x=dict()

    x.setdefault('a',set()).add(5)

    print(x) #{'a': {5}}

    x.setdefault('a',set()).add(6)

    print(x) #{'a': {5, 6}}

edited Mar 24, 2020 at 17:59

answered Mar 23, 2020 at 19:59

Utsav Chokshi

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