How to Increment Values in a Map

Question

I am wrapping my head around state in Clojure. I come from languages where state can be mutated. For example, in Python, I can create a dictionary, put some string => integer pairs inside, and then walk over the dictionary and increment the values.

How would I do this in idiomatic Clojure?

Answer 1

To slightly improve @Michiel Brokent's answer. This will work if the key already doesn't present.

(update my-map :a #(if (nil? %) 1 (inc %)))