Go Basics

Go for Loops

Go has one loop keyword. See its four forms: counting, while-style, infinite and range.

Beginner
3 min read
1 runnable example

What you'll learn

The three-part for
for as a while loop
range

Run code →

for i := 1; i <= 3; i++

1print

2print

3print

4stop

The loop ends when i <= 3 is false.

One keyword, four forms

Go has one loop keyword: for. It can count with three parts, repeat while a condition is true, run forever until break, or visit every item with range.

The first loop has a start, a condition and a step. The second has only a condition, like while in other languages. The third has nothing and ends with break. range over a string gives the position and the character of each letter.

Key points

for i := 1; i <= 3; i++ counts.
for condition { } works like while.
range visits every item.

Runnable Go example

Run code →

main.go

package main

import "fmt"

func main() {
	for i := 1; i <= 3; i++ {
		fmt.Println("for:", i)
	}

	countdown := 3
	for countdown > 0 { // a while loop
		fmt.Println("while:", countdown)
		countdown--
	}

	total := 0
	for { // an infinite loop, left with break
		total += 10
		if total >= 30 {
			break
		}
	}
	fmt.Println("loop result:", total)

	for index, letter := range "Go" {
		fmt.Println(index, string(letter))
	}
}

Get a Run button for this example Result of running the code

for: 1
for: 2
for: 3
while: 3
while: 2
while: 1
loop result: 30
0 G
1 o

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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