How to Delete Element from Slice in Go: Simple Guide

To delete an element from a slice in Go, use slicing and the append function to combine parts before and after the element. For example, slice = append(slice[:index], slice[index+1:]...) removes the element at index.

Syntax

The common syntax to delete an element at a specific index from a slice slice is:

• slice[:index]: selects all elements before the index.
• slice[index+1:]: selects all elements after the index.
• append(slice[:index], slice[index+1:]...): joins these two parts, effectively removing the element at index.

go

slice = append(slice[:index], slice[index+1:]...)

Example

This example shows how to delete the element at index 2 from a slice of integers.

go

package main

import "fmt"

func main() {
    numbers := []int{10, 20, 30, 40, 50}
    index := 2 // element 30

    // Delete element at index 2
    numbers = append(numbers[:index], numbers[index+1:]...)

    fmt.Println(numbers) // Output: [10 20 40 50]
}

Output

[10 20 40 50]

Common Pitfalls

Common mistakes when deleting from slices include:

• Not using the ... operator after the second slice in append, which causes a compile error.
• Trying to delete an element with an index out of range, which causes a runtime panic.
• Modifying the slice while iterating over it without adjusting the index, which can skip elements.

go

package main

import "fmt"

func main() {
    nums := []int{1, 2, 3, 4}
    index := 1

    // Wrong: missing ... causes compile error
    // nums = append(nums[:index], nums[index+1:])

    // Correct:
    nums = append(nums[:index], nums[index+1:]...)
    fmt.Println(nums) // Output: [1 3 4]
}

Output

[1 3 4]

Quick Reference

Remember these tips when deleting from slices:

• Use append(slice[:i], slice[i+1:]...) to remove element at i.
• Check that i is within slice bounds.
• Use the ... operator to expand the second slice.
• Deleting changes the slice length and order.

Key Takeaways

Use append with slicing and the ... operator to delete an element from a slice.

Always ensure the index is valid to avoid runtime errors.

Deleting an element shifts later elements left and reduces slice length.

Forget the ... operator after the second slice causes compile errors.

Avoid modifying a slice while iterating without adjusting indexes.