retrying something 3 times before throwing an exception - in clojure

Question

I don\'t know how to implement this piece of Python code in Clojure

for i in range(3):
    try:
        ......
    except e:
        if i == 2:
            raise         


        

Answer 1

Similar to Marcyk's answer, but no macro trickery:

(defn retry
  [retries f & args]
  (let [res (try {:value (apply f args)}
                 (catch Exception e
                   (if (zero? retries)
                     (throw e)
                     {:exception e})))]
    (if (:exception res)
      (recur (dec retries) f args)
      (:value res))))

Slightly complicated because you can't recur inside a catch clause. Note that this takes a function:

(retry 3 (fn [] 
          (println "foo") 
          (if (zero? (rand-int 2))
              (throw (Exception. "foo"))
              2)))
=>
foo ;; one or two or three of these
foo
2