Go Print Statements

Go fmt.Print() function

Let us take an example to demonstrate the fmt.Print() function

// Program to illustrate Print() function

package main

import "fmt"

// prints output in same lines
func main() {

	name := "Chandler Bing"

	fmt.Print("Hello", name)
	fmt.Print("Welcome to Go Programming")

}

Output

HelloChandler BingWelcome to Go Programming

Notice -

• The output messages are printed in a same line
• It does not additional space while printing the values of a variable.

Go fmt.Println() method

Let us take an example to demonstrate the fmt.Println() function

// Program to illustrate Println() function

package main

import "fmt"

// prints output in different lines
func main() {

	name := "Chandler Bing"

	fmt.Println("Hello", name)
	fmt.Println("Welcome to Go Programming")

}

Output

Hello Chandler Bing
Welcome to Go Programming

Notice -

• The output messages are printed on a different lines
• It also adds an additional space while printing the values of a variable.

Go println() Method

Suppose that we want to print the value of a variable inside a piece of text. If you only use what we have learned so far, you would have to write something like this:

package main

func main() {
	var myNumber int = 42
	println("My favorite number is", myNumber, "!")
}

My favorite number is 42 !

Notice -

• it adds extra spaces that we do not necessarily want.

To solve this problem, Go provides a function called fmt.Printf that allows you to print a formatted string efficiently.

Why there are two println and Println functions?

If you are asking yourself why there are two functions with the same behavior (println and Println), it is because println is a built-in function, while Println is a function from the fmt package. The former may be removed in the future, so it is better to use the latter.

For the rest of this tutorial, we will consistently use the fmt package.

Formatted strings

A formatted string is a string that contains placeholders (usually % followed by a letter) for values that will be replaced by the values of variables.

For instance, the string "My favorite number is %d!" contains a placeholder for an integer value (%d). The most common placeholders are:

• %d for integers,
• %f for floating-point numbers (you can specify the number of digits after the decimal point, e.g. %.2f for two digits),
• %s for strings,
• %t for booleans.

Go fmt.Printf() method

To choose the values that will replace the placeholders, you have to pass them as arguments to the Printf function from the fmt package.

package main

import "fmt"

func main() {
	var myNumber int = 42
	fmt.Printf("My favorite number is %d!\n", myNumber)
}

Output

My favorite number is 42!

Notice -

• The \n at the end of the string is a special character that represents a newline.
• It was automatically added by the println function, but we have to add it manually when using Printf.

More examples

Here are a few more examples of formatted strings:

package main

import "fmt"

func main() {
	const pi float64 = 22. / 7.
	const message string = "Hello, World!"
	const myBool bool = false

	fmt.Printf("Pi is approximately %.2f, tau is approximately %.2f\n", pi, 2*pi)
	fmt.Printf("The message is \"%s\".\n", message)
	fmt.Printf("This sentence is %t.\n", myBool)
}

Output

Pi is approximately 3.14, tau is approximately 6.29
The message is "Hello, World!".
This sentence is false.

Note: We used \" to print a double quote since " would have ended the formatted string instead. It is similar to the \n we used to print a newline. Other special characters include \t for a tabulation and \r for a carriage return.

The Print and Println functions

In order to print basic strings (just as before with println), you can use the Print and Println functions from the fmt package. The difference between them is that Println automatically adds a newline at the end of the string, while Print does not.