How to fmt.Printf an integer with thousands comma

Question

Does Go\'s fmt.Printf support outputting a number with the thousands comma?

fmt.Printf(\"%d\", 1000) outputs 1000, what format

Answer 1

Here's a simple function using regex:

import (
    "regexp"
)

func formatCommas(num int) string {
    str := fmt.Sprintf("%d", num)
    re := regexp.MustCompile("(\\d+)(\\d{3})")
    for n := ""; n != str; {
        n = str
        str = re.ReplaceAllString(str, "$1,$2")
    }
    return str
}

Example:

fmt.Println(formatCommas(1000))
fmt.Println(formatCommas(-1000000000))

Output:

1,000
-1,000,000,000

https://play.golang.org/p/vnsAV23nUXv