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How to efficiently concatenate strings in go language?

Maheshwar Ligade's photo
Maheshwar Ligade
·May 2, 2023·

3 min read

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Table of contents

  • Introduction
  • The Naive Way: + Operator
  • The Better Way: strings.Join
  • The Best Way: bytes.Buffer
  • Comparison of Performance
  • Conclusion

Introduction

Concatenating string is a common operation in programming, and it is important to do it efficiently to avoid wasting memory and CPU cycles. In this article, we will look at several ways to concatenate strings in Go and compare their performance.

The Naive Way: + Operator

The simplest way to concatenate strings in Go is to use the + operator. Here's an example:

package main

import "fmt"

func main() {
    s := "hello" + " " + "world"
    fmt.Println(s)
}

This works fine for small strings, but it is not very efficient for large strings because it creates a new string every time the + operator is used. For example, if you wanted to concatenate a large number of strings, you would end up creating many intermediate strings, which would waste memory and CPU cycles.

The Better Way: strings.Join

A better way to concatenate strings in Go is to use the strings.Join function. Here's an example:

package main

import (
    "fmt"
    "strings"
)

func main() {
    s := []string{"hello", "world"}
    fmt.Println(strings.Join(s, " "))
}

This function takes a slice of strings and a separator string, and it concatenates the strings with the separator in between. This approach is more efficient than using the + operator because it avoids creating intermediate strings.

The Best Way: bytes.Buffer

The most efficient way to concatenate strings in Go is to use the bytes.Buffer type. Here's an example:

package main

import (
    "bytes"
    "fmt"
)

func main() {
    var buf bytes.Buffer
    buf.WriteString("hello")
    buf.WriteString(" ")
    buf.WriteString("world")
    fmt.Println(buf.String())
}

This approach uses a buffer to accumulate the strings, which avoids creating intermediate strings and results in the most efficient concatenation.

Comparison of Performance

To compare the performance of these three approaches, we can use the following benchmark code:

package main

import (
    "bytes"
    "strings"
    "testing"
)

func BenchmarkPlusOperator(b *testing.B) {
    for i := 0; i < b.N; i++ {
        _ = "hello" + " " + "world"
    }
}

func BenchmarkStringsJoin(b *testing.B) {
    s := []string{"hello", "world"}
    for i := 0; i < b.N; i++ {
        _ = strings.Join(s, " ")
    }
}

func BenchmarkBytesBuffer(b *testing.B) {
    var buf bytes.Buffer
    s := []string{"hello", "world"}
    for i := 0; i < b.N; i++ {
        for _, str := range s {
            buf.WriteString(str)
            buf.WriteString(" ")
        }
        _ = buf.String()
        buf.Reset()
    }
}

Running this benchmark shows that the bytes.Buffer approach is the fastest, followed by the strings.Join approach, and finally the + operator approach.

Conclusion

When concatenating strings in Go, it is important to do it efficiently to avoid wasting memory and CPU cycles. The + operator is the simplest approach, but it can be inefficient for large strings. The strings.Join function is more efficient because it avoids creating intermediate strings. The most efficient approach is to use the bytes.Buffer type, which avoids creating intermediate strings altogether.

I hope this helps, you!!

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