Go – Iterate over Slice using Range

In Go, the range keyword is used to iterate over slices, allowing you to access both the index and value of each element. This provides a concise and readable way to traverse and process slices.

In this tutorial, we will explore how to use range with slices in Go, demonstrate practical examples, and provide detailed explanations.

Key Features of range with Slices

  • Index and Value: The range loop provides both the index and value of each element in the slice.
  • Index Only: You can ignore the value by using the blank identifier (_).
  • Value Only: You can ignore the index and retrieve only the value.

Examples of Using range with Slices

1. Access Both Index and Value

This example demonstrates how to access both the index and value of each element in a slice:

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package main

import "fmt"

func main() {
    // Define a slice
    numbers := []int{10, 20, 30, 40, 50}

    // Use range to iterate over the slice
    for index, value := range numbers {
        fmt.Printf("Index: %d, Value: %d\n", index, value)
    }
}

Explanation

  1. Define Slice: A slice numbers is initialized with integers {10, 20, 30, 40, 50}.
  2. Iterate with Range: The range keyword is used to iterate over the slice, returning both the index and value of each element.
  3. Print Results: The index and value are printed in each iteration using fmt.Printf.

Output

2. Access Only the Value

This example demonstrates how to access only the values in a slice:

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package main

import "fmt"

func main() {
    // Define a slice
    numbers := []int{5, 10, 15, 20, 25}

    // Use range to iterate and access only the value
    for _, value := range numbers {
        fmt.Printf("Value: %d\n", value)
    }
}

Explanation

  1. Define Slice: A slice numbers is initialized with integers {5, 10, 15, 20, 25}.
  2. Ignore Index: The blank identifier (_) is used to ignore the index returned by range.
  3. Access Value: The value variable holds the current element in each iteration.
  4. Print Results: The value is printed in each iteration using fmt.Printf.

Output

3. Access Only the Index

This example demonstrates how to access only the indices in a slice:

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package main

import "fmt"

func main() {
    // Define a slice
    numbers := []int{2, 4, 6, 8, 10}

    // Use range to iterate and access only the index
    for index := range numbers {
        fmt.Printf("Index: %d\n", index)
    }
}

Explanation

  1. Define Slice: A slice numbers is initialized with integers {2, 4, 6, 8, 10}.
  2. Ignore Value: The value returned by range is ignored by omitting it in the loop declaration.
  3. Access Index: The index variable holds the current index in each iteration.
  4. Print Results: The index is printed in each iteration using fmt.Printf.

Output

Points to Remember

  • Index and Value: The range loop provides both the index and value for each element in a slice.
  • Blank Identifier: Use the blank identifier (_) to ignore either the index or value.
  • Immutable Values: Modifying the value variable in the loop does not change the slice. To update the slice, use the index directly.
  • Flexible Syntax: range is versatile and works seamlessly with slices of any type.