How to efficiently concatenate strings in Go?

Question

In Go, a string is a primitive type, which means it is read-only, and every manipulation of it will create a new string. So if I want to concatenate strings many times without knowing the length of the resulting string, what's the best way to do it? The naive way would be: s := "" for i := 0; i < 1000; i++ { s += getShortStringFromSomewhere() } return s but that does not seem very efficient.

Lex Hoffman · Accepted Answer

Note added in 2018 The best way is to use the bytes package. It has a Buffer type which implements io.Writer. package main import ( "bytes" "fmt" ) func main() { var buffer bytes.Buffer for i := 0; i < 1000; i++ { buffer.WriteString("a") } fmt.Println(buffer.String()) } This does it in O(n) time.

Chris Gregori · Answer

here is a library function in the strings package called Join: http://golang.org/pkg/strings/#Join A look at the code of Join shows a similar approach to Append function Kinopiko wrote: https://golang.org/src/strings/strings.go#L420 Usage: import ( "fmt"; "strings"; ) func main() { s := []string{"this", "is", "a", "joined", "string
"}; fmt.Printf(strings.Join(s, " ")); } $ ./test.bin this is a joined string

Go Language

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