Initializing a dictionary in python with a key value and no corresponding values

python dictionary initialization key
user2989027 picture user2989027 · Nov 19, 2013 · Viewed 213k times · Source

I was wondering if there was a way to initialize a dictionary in python with keys but no corresponding values until I set them. Such as:

Definition = {'apple': , 'ball': }

and then later i can set them:

Definition[key] = something

I only want to initialize keys but I don't know the corresponding values until I have to set them later. Basically I know what keys I want to add the values as they are found. Thanks.

Answer

codegeek picture codegeek · Nov 19, 2013

Use the fromkeys function to initialize a dictionary with any default value. In your case, you will initialize with None since you don't have a default value in mind.

empty_dict = dict.fromkeys(['apple','ball'])

this will initialize empty_dict as:

empty_dict = {'apple': None, 'ball': None}

As an alternative, if you wanted to initialize the dictionary with some default value other than None, you can do:

default_value = 'xyz'
nonempty_dict = dict.fromkeys(['apple','ball'],default_value)

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