我有以下哈希映射集合：
{a:"Completed" b:1 c:"Friday" d:4}
{a:"Started" b:1 c:"Monday" d:4}
{a:"In Progress" b:1 c:"Sunday" d:1}
{a:"Completed" b:3 c:"Tuesday" d:9}
如何将其转换为 clojure 中的 CSV 文件？
IE
a,b,c,d
Completed,1,Friday,4
Started,1,Monday,4
In Progress,1,Sunday,1
Completed,3,Tuesday,9
对此的任何帮助将不胜感激。
您没有明确表示您是从 JSON 开始的，但我们假设您是。在这种情况下，我将使用cheshire
解析您的 JSON 字符串以获取表示您的数据的地图向量。为了简单起见，我们假设您已经这样做了，并且只使用var调用data来避免使示例混乱。
现在我们可以创建一个向量向量，然后使用 clojure.data.csv将结果保存到文件中。
您可以使用lein try在 REPL 上尝试一下。lein try如果您还没有它，请
按照设置说明进行操作，然后运行lein try clojure.data.csv 0.1.2. 一旦您进入具有此依赖关系的 REPL：
(require '[clojure.data.csv :as csv] '[clojure.java.io :as io])
(def data
[{:a "Completed" :b 1 :c "Friday" :d 4}
{:a "Started" :b 1 :c "Monday" :d 4}
{:a "In Progress" :b 1 :c "Sunday" :d 1}
{:a "Completed" :b 3 :c "Tuesday" :d 9}])
(defn write-csv [path row-data]
(let [columns [:a :b :c :d]
headers (map name columns)
rows (mapv #(mapv % columns) row-data)]
(with-open [file (io/writer path)]
(csv/write-csv file (cons headers rows)))))
(write-csv "/tmp/results.csv" data)
现在您可以看到您的手工制作的结果：
$ cat /tmp/results.csv
a,b,c,d
Completed,1,Friday,4
Started,1,Monday,4
In Progress,1,Sunday,1
Completed,3,Tuesday,9
我阅读了所有答案，但我想要更通用和可重用的解决方案。
这是我想出的。您可以通过单独或一起使用write-csvand 。更重要的是，您不需要对标头进行硬编码。只需传递您的地图矢量，您就应该准备就绪。maps->csv-datawrite-csv-from-maps
A. DIY 方法
(require '[clojure.data.csv :as csv]
'[clojure.java.io :as io])
(defn write-csv
"Takes a file (path, name and extension) and
csv-data (vector of vectors with all values) and
writes csv file."
[file csv-data]
(with-open [writer (io/writer file)]
(csv/write-csv writer csv-data)))
(defn maps->csv-data
"Takes a collection of maps and returns csv-data
(vector of vectors with all values)."
[maps]
(let [columns (-> maps first keys)
headers (mapv name columns)
rows (mapv #(mapv % columns) maps)]
(into [headers] rows)))
(defn write-csv-from-maps
"Takes a file (path, name and extension) and a collection of maps
transforms data (vector of vectors with all values)
writes csv file."
[file maps]
(->> maps maps->csv-data (write-csv file)))
B. 语义 CSV 方法
或者，您可以使用semantic-csv库。
maps->csv-data然后会变成semantic-csv.core/vectorize
(require '[clojure.data.csv :as csv]
'[clojure.java.io :as io]
'[semantic-csv.core :as sc])
(defn write-csv
"Takes a file (path, name and extension) and
csv-data (vector of vectors with all values) and
writes csv file."
[file csv-data]
(with-open [writer (io/writer file)]
(csv/write-csv writer csv-data)))
(defn write-csv-from-maps
"Takes a file (path, name and extension) and a collection of maps
transforms data (vector of vectors with all values)
writes csv file."
[file maps]
(->> maps sc/vectorize (write-csv file)))
--
最后：
(def data
[{:a "Completed" :b 1 :c "Friday" :d 4}
{:a "Started" :b 1 :c "Monday" :d 4}
{:a "In Progress" :b 1 :c "Sunday" :d 1}
{:a "Completed" :b 3 :c "Tuesday" :d 9}])
(write-csv "/tmp/results.csv" data)
希望对某人有用！
使用data.json将 json 转换为 clojure 映射序列。
使用映射解构转换为字符串序列：(map #(let [{a :a b :b c :c d :d} %] (str a "," b "," c "," d, "\n")) <your sequence of clojure maps>).
将字符串序列转储到文件中
(def data [{:a "Completed" :b 1 :c "Friday" :d 4}
{:a "Started" :b 1 :c "Monday" :d 4}
{:a "In Progress" :b 1 :c "Sunday" :d 1}
{:a "Completed" :b 3 :c "Tuesday" :d 9}])
(for [i (range (count data))]
(if (= i 0)
(do
(spit "data.csv" (str (clojure.string/join "," (map name (keys (data i)))) "\n") :append true)
(spit "data.csv" (str (clojure.string/join "," (vals (data i))) "\n") :append true))
(spit "data.csv" (str (clojure.string/join "," (vals (data i))) "\n") :append true)))
要查看结果：
$ cat data.csv
c,b,d,a
Friday,1,4,Completed
Monday,1,4,Started
Sunday,1,1,In Progress
Tuesday,3,9,Completed
这个答案更好，因为这种方法从数据中获取所有内容，您不必对任何内容进行硬编码。而且这种方法不使用任何额外的库，除了clojure.string/join.
使用clojure-csv库，轻松读写格式良好的 csv。