Equivalent of Python string.format in Go?

Question

In Python, you can do this:

\"File {file} had error {error}\".format(file=myfile, error=err)

or this:

\"File %(file)s had e         


        

Answer 1

The parameter can also be a map, so the following function would work if you don't mind parsing every error format every time you use it:

package main

import (
    "bytes"
    "text/template"
    "fmt"
)

func msg(fmt string, args map[string]interface{}) (str string) {
    var msg bytes.Buffer

    tmpl, err := template.New("errmsg").Parse(fmt)

    if err != nil {
        return fmt
    }

    tmpl.Execute(&msg, args)
    return msg.String()
}

func main() {
    fmt.Printf(msg("File {{.File}} has error {{.Error}}\n", map[string]interface{} {
        "File": "abc",
        "Error": "def",
    }))
}

It's still a little wordier than I would have liked, but it's better than some other options, I suppose. You could turn map[string]interface{} into a local type and reduce it further to:

type P map[string]interface{}

fmt.Printf(msg("File {{.File}} has error {{.Error}}\n", P{
        "File": "abc",
        "Error": "def",
    }))