Formatting Strings in Go

Go follows the printf tradition from the C language. In my opinion, string formatting/interpolation in Go is less elegant than Python's f-strings, unfortunately.

• fmt.Printf - Prints a formatted string to standard out.

• fmt.Sprintf() - Returns the formatted string

These following "formatting verbs" work with the formatting functions above:

Default Representation

The %v variant prints the Go syntax representation of a value, it's a nice default.

s := fmt.Sprintf("I am %v years old", 10)
// I am 10 years old

s := fmt.Sprintf("I am %v years old", "way too many")
// I am way too many years old

If you want to print in a more specific way, you can use the following formatting verbs:

String

s := fmt.Sprintf("I am %s years old", "way too many")
// I am way too many years old

Integer

s := fmt.Sprintf("I am %d years old", 10)
// I am 10 years old

Float

s := fmt.Sprintf("I am %f years old", 10.523)
// I am 10.523000 years old

// The ".2" rounds the number to 2 decimal places
s := fmt.Sprintf("I am %.2f years old", 10.523)
// I am 10.52 years old

If you're interested in all the formatting options, you can look at the fmt package's docs.

Assignment

Create a new variable called msg on line 9 and use the appropriate formatting function to return a string that contains the following:

Hi NAME, your open rate is OPENRATE percentNEWLINE

• Replace NAME with the variable name.

• Replace OPENRATE with the variable openRate rounded to the nearest "tenths" place, e.g. 10.523 should be rounded down to 10.5.

• The word percent should appear as part of the string following the open rate value.

• Replace NEWLINE with the newline \n escape sequence.

With the inputs "Jimmy McGill" and 2.5, the expected output would be:

Hi Jimmy McGill, your open rate is 2.5 percent

main.go

package main

import "fmt"

func main() {
	const name = "Saul Goodman"
	const openRate = 30.5

	// ?

	// don't edit below this line

	fmt.Print(msg)
}

Solution

main.go (solution)

package main

import "fmt"

func main() {
	const name = "Saul Goodman"
	const openRate = 30.5

	msg := fmt.Sprintf("Hi %v, your open rate is %.1f percent \n", name, openRate)

	// don't edit below this line

	fmt.Print(msg)
}