How to Filter a Map Based on Keys in Go - Step by Step Examples

How to Filter a Map Based on Keys in Go ?

Answer

To filter a map based on keys in Go, you can iterate over the map and add key-value pairs that meet the filter criteria to a new map. This method allows you to create a subset of the original map based on specific key conditions.

✐ Examples

1 Filtering a Map Based on Key Range

We can filter a map based on a range of keys in Go by iterating over the map and adding key-value pairs that fall within the specified range to a new map.

For example,

We start by importing the fmt package, which provides the necessary functions for input-output operations.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We declare an empty map named filteredMap to store the filtered key-value pairs.
We define the lower and upper bounds of the key range.
We iterate over the original map using a for loop and check if each key falls within the specified range.
We add the key-value pairs that meet the condition to the filteredMap.
We print the filtered map to the console using the fmt.Println function to verify the filtering.

Go Program

package main

import "fmt"

func main() {
    // Declare and initialize a map
    myMap := map[int]string{
        1: "one",
        2: "two",
        3: "three",
        4: "four",
        5: "five",
    }

    // Declare an empty map to store the filtered key-value pairs
    filteredMap := make(map[int]string)

    // Define the key range
    lowerBound := 2
    upperBound := 4

    // Iterate over the original map and filter based on the key range
    for key, value := range myMap {
        if key >= lowerBound && key <= upperBound {
            filteredMap[key] = value
        }
    }

    // Print the filtered map
    fmt.Println("Filtered Map by Key Range:")
    for key, value := range filteredMap {
        fmt.Printf("%d: %s\n", key, value)
    }
}

Output

Filtered Map by Key Range:
2: two
3: three
4: four

2 Filtering a Map Based on Specific Keys

We can filter a map based on specific keys in Go by iterating over the map and adding key-value pairs that match the specified keys to a new map.

For example,

We start by importing the fmt and sort packages, which provide the necessary functions for input-output operations and sorting.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We declare an empty map named filteredMap to store the filtered key-value pairs.
We define a slice of specific keys that we want to filter the map by.
We iterate over the original map using a for loop and check if each key matches one of the specified keys.
We add the key-value pairs that meet the condition to the filteredMap.
We print the filtered map to the console using the fmt.Println function to verify the filtering.

Go Program

package main

import "fmt"

func main() {
    // Declare and initialize a map
    myMap := map[int]string{
        1: "one",
        2: "two",
        3: "three",
        4: "four",
        5: "five",
    }

    // Declare an empty map to store the filtered key-value pairs
    filteredMap := make(map[int]string)

    // Define the specific keys to filter by
    keysToFilter := []int{1, 3, 5}

    // Iterate over the original map and filter based on the specific keys
    for key, value := range myMap {
        for _, k := range keysToFilter {
            if key == k {
                filteredMap[key] = value
                break
            }
        }
    }

    // Print the filtered map
    fmt.Println("Filtered Map by Specific Keys:")
    for key, value := range filteredMap {
        fmt.Printf("%d: %s\n", key, value)
    }
}

Output

Filtered Map by Specific Keys:
1: one
3: three
5: five

3 Filtering a Map with String Keys Based on Prefix

We can filter a map with string keys based on a specific prefix in Go by iterating over the map and adding key-value pairs that have keys starting with the given prefix to a new map.

For example,

We start by importing the fmt and strings packages, which provide the necessary functions for input-output operations and string manipulations.
We declare and initialize a map named myMap with some key-value pairs. In this example, the map has string keys and string values.
We declare an empty map named filteredMap to store the filtered key-value pairs.
We define a prefix string that we want to filter the map by.
We iterate over the original map using a for loop and check if each key starts with the specified prefix.
We add the key-value pairs that meet the condition to the filteredMap.
We print the filtered map to the console using the fmt.Println function to verify the filtering.

Go Program

package main

import (
    "fmt"
    "strings"
)

func main() {
    // Declare and initialize a map
    myMap := map[string]string{
        "apple": "fruit",
        "banana": "fruit",
        "carrot": "vegetable",
        "apricot": "fruit",
        "blueberry": "fruit",
    }

    // Declare an empty map to store the filtered key-value pairs
    filteredMap := make(map[string]string)

    // Define the prefix to filter by
    prefix := "ap"

    // Iterate over the original map and filter based on the prefix
    for key, value := range myMap {
        if strings.HasPrefix(key, prefix) {
            filteredMap[key] = value
        }
    }

    // Print the filtered map
    fmt.Println("Filtered Map by Prefix:")
    for key, value := range filteredMap {
        fmt.Printf("%s: %s\n", key, value)
    }
}

Output

Filtered Map by Prefix:
apple: fruit
apricot: fruit

Summary

In this tutorial, we learned How to Filter a Map Based on Keys in Go language with well detailed examples.

◀ Previous Next ▶

Go Tutorials

Go Programs

Go How-Tos

How to Filter a Map Based on Keys in Go - Step by Step Examples