How to split Golang strings without deleting separator?

Question

According to the answer at How to split a string and assign it to variables in Golang? splitting a string results in an array of strings where the separator is not present in any of the strings in the array. Is there a way to split strings such that the separator is on the last line of a given string?

e.x.

s := strings.split("Potato:Salad:Popcorn:Cheese", ":")
for _, element := range s {
    fmt.Printf(element)
}

outputs:

Potato
Salad
Popcorn
Cheese

I wish to output the following instead:

Potato:
Salad:
Popcorn:
Cheese

I know I could theoretically append ":" to the end of each element except for the last, but I'm looking for a more general, elegant solution if possible.

You can try to search for :, and get the sub string via index, without a split() method. — Eric
– Eric, Commented Aug 15, 2018 at 1:10
you can use Regex golang.org/pkg/regexp/#Regexp.FindAllString — sayboras
– sayboras, Commented Aug 15, 2018 at 1:15

maerics · Accepted Answer · 2018-08-15 02:25:31Z

14

You are looking for SplitAfter.

s := strings.SplitAfter("Potato:Salad:Popcorn:Cheese", ":")
  for _, element := range s {
  fmt.Println(element)
}
// Potato:
// Salad:
// Popcorn:
// Cheese

Go Playground

edited Aug 15, 2018 at 2:25

maerics

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answered Aug 15, 2018 at 2:05

daplho

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Comments

reticentroot · Accepted Answer · 2018-08-16 03:12:43Z

1

The answer above by daplho great and simple. Sometimes I just like to provide an alternative to remove the magic of a function

package main

import "fmt"

var s = "Potato:Salad:Popcorn:Cheese"

func main() {
    a := split(s, ':')
    fmt.Println(a)
}

func split(s string, sep rune) []string {
    var a []string
    var j int
    for i, r := range s {
        if r == sep {
            a = append(a, s[j:i+1])
            j = i + 1
        }
    }
    a = append(a, s[j:])
    return a
}

https://goplay.space/#h9sDd1gjjZw

As a side note, the standard lib version is better than the hasty one above

goos: darwin
goarch: amd64
BenchmarkSplit-4             5000000           339 ns/op
BenchmarkSplitAfter-4       10000000           143 ns/op

So go with that lol

edited Aug 16, 2018 at 3:12

answered Aug 16, 2018 at 3:03

reticentroot

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1 Comment

daplho Over a year ago

As golang is open-source, a peek under the hood readily reveals SplitAfter's implementation. It utilizes the genSplit function: go.googlesource.com/go/+/master/src/strings/strings.go#240

Anshu · Accepted Answer · 2019-06-01 19:00:13Z

0

Try this to get the proper result.

package main

    import (
        "fmt"
        "strings"
    )

    func main() {
        str := "Potato:Salad:Popcorn:Cheese"
        a := strings.SplitAfter(str, ":")
        for i := 0; i < len(a); i++ {
            fmt.Println(a[i])
        }
    }

edited Jun 1, 2019 at 19:00

answered Jun 1, 2019 at 18:18

Anshu

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