Deleting an element from a slice in Go

The Problem

You don’t know how to delete an element from a slice in Go.

The Solution

If you know the index of the element(s) that you want to delete from a slice, you can use the Delete function from the slices package.

Note: The slices.Delete function is O(len(s)-i), where i represents the start of the range to be deleted. If you need to delete many items, it is better to delete them all in a single call than to delete one item at a time. This function also expects the input to be valid.

package main

import (
	"fmt"
	"slices"
)

func main() {
	letters := []string{"a", "b", "c", "d", "e"}
	letters = slices.Delete(letters, 1, 4)
	fmt.Println(letters)
}

This prints:

[a e]

Attempting to delete an invalid range will cause a panic, as in the example below:

package main

import (
	"fmt"
	"slices"
)

func main() {
	letters := []string{"a", "b", "c", "d", "e"}
	letters = slices.Delete(letters, 1, 10)
}

Because 10 is an invalid index, this returns the following panic:

panic: runtime error: slice bounds out of range [:10:5]

Searching for Elements

If you want to search for specific elements in a slice, you can use the slices.DeleteFunc instead.

For example, you could search for all the even numbers in a slice as follows:

package main

import (
	"fmt"
	"slices"
)

func main() {
	example := []int{0, 1, 2, 3, 4, 5, 6}
	example = slices.DeleteFunc(example, func(n int) bool {
		return n%2 != 0 // Remove odd numbers.
	})

	fmt.Println(example)
}

This prints an output of the slice with the odd numbers removed:

[0 2 4 6]

Note: This example passes the func(n int) filter function to slices.DeleteFunc. Because this is a generic filter function, its argument must match the type of the slice. In this case, it accepts an int because example is a slice of integers. If you instead wanted to filter a specific string from strings, you would change the argument of the filter function to string:

package main

import (
	"fmt"
	"slices"
)

func main() {
	example := []string{"a", "b", "c"}
	example = slices.DeleteFunc(example, func(s string) bool {
		return s == "b"
	})

	fmt.Println(example)
}

This would print:

[a c]

Further Reading

• The Go slices package
• The Go Slices: usage and internals blog post