How to alphabetize a csv file using Go?

Question

I'm trying to order a .csv file with a series of names alphabetically using Go, based off of the last name, which is in the first column. I've searched all over, but I can't seem to find a way to do it. Is there a way to do this, while holding onto the other values in the same row? I have three .csv files with the same names, but I have to shuffle them in order to complete my task (a random table seating algorithm). I want to be able to put them back into a defined alphabetical order so that I can be sure that people don't sit with each other consecutively.

Thanks in advance. :)

EDIT: Might be worth showing my function I use to shuffle it:

func Shuffle(slice []Person) []Person {
r := rand.New(rand.NewSource(time.Now().Unix()))
ret := make([]Person, len(slice))
n := len(slice)
for i := 0; i < n; i++ {
    randIndex := r.Intn(len(slice))
    ret[i] = slice[randIndex]
    slice = append(slice[:randIndex], slice[randIndex+1:]...)
}
return ret

The Person[] slice is just a struct that holds a first and last name.

Answer 1

Go's sort package comes with a great example. See an amended implementation that should do what you're asking about.

package main

import (
    "encoding/csv"
    "fmt"
    "io"
    "log"
    "sort"
    "strings"
)

// Unsorted sample data
var unsorted = `Balaam,Wileen,Saint Louis
Meachan,Lothaire,Lefengzhen
Scoggin,Ivonne,Pag
Hawarden,Audrye,Leiria
Claypool,Biddy,Maiorca
Stanford,Douglas,Báguanos
Petriello,Yvor,Obryte
Hatter,Margette,Luoping
Pepall,Linzy,Hucun
Carter,Kit,Parungjawa
`

type Person struct {
    Lastname  string
    Firstname string
    City      string
}

// Create a new Person record from a given string slice
func NewPerson(fields []string) (p Person, err error) {
    if len(fields) < 3 {
        return p, fmt.Errorf("not enough data for Person")
    }
    p.Lastname = fields[0]
    p.Firstname = fields[1]
    p.City = fields[2]
    return
}

// ByLastname implements sort.Interface for []Person based on the Lastname field.
type ByLastname []Person

func (a ByLastname) Len() int           { return len(a) }
func (a ByLastname) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ByLastname) Less(i, j int) bool { return a[i].Lastname < a[j].Lastname }

func main() {
    // Open unsorted CSV from string
    r := csv.NewReader(strings.NewReader(unsorted))

    var people []Person

    for {
        // Read CSV line by line
        record, err := r.Read()
        if err == io.EOF {
            break
        }
        if err != nil {
            log.Fatal(err)
        }

        // Create Person from line in CSV
        person, err := NewPerson(record)
        if err != nil {
            continue
        }
        people = append(people, person)
    }

    // Sort CSV by Lastname
    sort.Sort(ByLastname(people))

    // Print to stdout
    for _, p := range people {
        fmt.Printf("%s %s from %s\n", p.Lastname, p.Firstname, p.City)
    }

    // Here you would write your CSV
}