Read csv into a list in clojure

Question

I know there are a lot of related questions, I have read them but still have not gained some fundamental understanding of how to read-process-write. Take the following function for example which uses clojure-csv library to parse a line

(defn take-csv
  "Takes file name and reads data."
  [fname]
  (with-open [file (reader fname)]
    (doseq [line (line-seq file)]
      (let [record (parse-csv line)]))))

What I would like to obtain is data read into some collection as a result of (def data (take-csv "file.csv")) and later to process it. So basically my question is how do I return record or rather a list of records.

Answer 1

"doseq" is often used for operations with side effect. In your case to create collection of records you can use "map":

(defn take-csv
  "Takes file name and reads data."
  [fname]
  (with-open [file (reader fname)]
    (doall (map (comp first csv/parse-csv) (line-seq file)))))

Better parse the whole file at ones to reduce code:

(defn take-csv
  "Takes file name and reads data."
  [fname]
  (with-open [file (reader fname)]
    (csv/parse-csv (slurp file))))

You also can use clojure.data.csv instead of clojure-csv.core. Only should rename parse-csv to take-csv in previous function.

(defn put-csv [fname table]
  (with-open [file (writer fname)]
    (csv/write-csv file table)))