Go String Formatting: Beyond `fmt.Sprintf()` – What are the Alternatives?

Equivalent of Python string.format in Go?

In Python, string interpolation using the format() method offers flexibility in ordering and replacing parameters. However, in Go, the fmt.Sprintf() function provides a more limited option, hindering internationalization (I18N). Is there a more suitable alternative that allows for independent parameter ordering?

Strings.Replacer

Utilizing strings.Replacer enables you to create your custom string formatter effectively.

func main() {
    file, err := "/data/test.txt", "file not found"

    log("File {file} had error {error}", "{file}", file, "{error}", err)
}

func log(format string, args ...string) {
    r := strings.NewReplacer(args...)
    fmt.Println(r.Replace(format))
}

Sample Output:

File /data/test.txt had error file not found

WiText/Template

The text/template package offers a template-based solution, though it can be more verbose than the Strings.Replacer approach.

type P map[string]interface{}

func main() {
    file, err := "/data/test.txt", 666

    log4("File {{.file}} has error {{.error}}", P{"file": file, "error": err})
}

func log4(format string, p P) {
    t := template.Must(template.New("").Parse(format))
    t.Execute(os.Stdout, p)
}

Sample Output:

File /data/test.txt has error 666

Explicit Argument Indices

fmt.Sprintf() supports explicit argument indices, allowing you to repeat the same index multiple times to substitute the same parameter. Learn more about this technique in the related question "Replace all variables in Sprintf with same variable."

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