Using Go to create text files from columns of a csv data frame - go

Question

I am trying to loop over a csv file and output text file titled after each row in the first column. Each text file is then be populated with data from the other rows for that column. I am able to print the contents of the csv to a text file, but I can not get the logic down using a for loop to grab the index of column one and use that to create/title a new .txt file.
package main
import (
"fmt"
"io"
"io/ioutil"
"log"
"os"
)
func main() {
fmt.Println("Enter file path to CSV: ")
var csvFile string
_, err := fmt.Scanln(&csvFile)
if err != nil {
log.Fatal("Cannot read input")
return
}
//open file
inFile, err := os.Open(csvFile)
if err != nil {
log.Fatal(err)
}
defer inFile.Close()
readMe, _ := ioutil.ReadAll(inFile)
blankFile, err := os.Create(`C:\temp\test.txt`)
if err != nil {
log.Fatal(err)
}
defer blankFile.Close()
//write data to text file
outFile, err := blankFile.Write(readMe)
if err == io.EOF {
log.Fatalln("Failed")
} else if err != nil {
log.Fatal(err)
}
//print bytes total
fmt.Println(outFile, " bytes printed")
}

Answer 1

Take multiple columns from a csv and print each column to a new text
file.
Loop over a csv and produce a new text file that will be titled after
each column in row #1. Each text file will then be populated with data
from the other rows for that column.
For example,
package main
import (
"encoding/csv"
"fmt"
"io"
"os"
"path/filepath"
)
func CsvFileToTxtFiles(inFile string) error {
in, err := os.Open(inFile)
if err != nil {
return err
}
defer in.Close()
r := csv.NewReader(in)
hdr, err := r.Read()
if err != nil {
return err
}
f := make([]*os.File, len(hdr))
w := make([]*csv.Writer, len(hdr))
pfx := filepath.Clean(inFile)
pfx = pfx[:len(pfx)-len(filepath.Ext(pfx))]
for i, col := range hdr {
var err error
f[i], err = os.Create(pfx + "." + col + ".txt")
if err != nil {
return err
}
defer f[i].Close()
w[i] = csv.NewWriter(f[i])
if err != nil {
return err
}
defer w[i].Flush()
}
for {
row, err := r.Read()
if err != nil {
if row == nil && err == io.EOF {
break
}
return err
}
for i, col := range row {
err := w[i].Write([]string{col})
if err != nil {
return err
}
}
}
for i := range hdr {
var err error
w[i].Flush()
err = w[i].Error()
if err != nil {
return err
}
err = f[i].Close()
if err != nil {
return err
}
}
return nil
}
func main() {
if len(os.Args) <= 1 {
usage := "usage: " + filepath.Base(os.Args[0]) + " FILE"
fmt.Fprintln(os.Stderr, usage)
return
}
inFile := os.Args[1]
err := CsvFileToTxtFiles(inFile)
if err != nil {
fmt.Fprintln(os.Stderr, err)
return
}
}
Output:
$ cat ioj.test.csv
one,two,three
1,2,3
11,22,33
$ go run ioj.go ioj.test.csv
$ cat ioj.test.one.txt
1
11
$ cat ioj.test.two.txt
2
22
$ cat ioj.test.three.txt
3
33
$