Replace Nth occurrence of string in golang
How do I replace the nth (in this case the second) finding of the string in golang? The following code replaces the example line optimismo from optimism
with o from optimism
when I want it to beoptimismo from
package main
import (
"fmt"
"strings"
)
func main() {
mystring := "optimismo from optimism"
excludingSecond := strings.Replace(mystring, "optimism", "", 1)
fmt.Println(excludingSecond)
}
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2 answers
For example,
package main
import (
"fmt"
"strings"
)
// Replace the nth occurrence of old in s by new.
func replaceNth(s, old, new string, n int) string {
i := 0
for m := 1; m <= n; m++ {
x := strings.Index(s[i:], old)
if x < 0 {
break
}
i += x
if m == n {
return s[:i] + new + s[i+len(old):]
}
i += len(old)
}
return s
}
func main() {
s := "optimismo from optimism"
fmt.Printf("%q\n", s)
t := replaceNth(s, "optimism", "", 2)
fmt.Printf("%q\n", t)
}
Output:
"optimismo from optimism"
"optimismo from "
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If you always know there will be two, you can use https://godoc.org/strings#Index to find the index of the first, then replace with everything, then finally concatenating them together.
https://play.golang.org/p/CeJFViNjgH
func main() {
search := "optimism"
mystring := "optimismo from optimism"
// find index of the first and add the length to get the end of the word
ind := strings.Index(mystring, search)
if ind == -1 {
fmt.Println("doesn't exist")
return // error case
}
ind += len(search)
excludingSecond := mystring[:ind]
// run replace on everything after the first one
excludingSecond += strings.Replace(mystring[ind:], search, "", 1)
fmt.Println(excludingSecond)
}
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