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Check For Specific Elements in a Map in Go

Last Updated : May 27, 2025

In Go, you can check whether a specific key exists in a map using the comma-ok idiom. This helps you avoid confusion between a missing key and a key with a zero value.

Checking for a Specific Key

Use the second return value from map access to determine if a key exists.

Example

This example checks if specific students are present in the map:

package main
import "fmt"

func main() {
    attendance := map[string]bool{
        "Anjali": true,
        "Rohit":  true,
    }

    name := "Rohit"
    if present, ok := attendance[name]; ok {
        fmt.Printf("%s is marked present: %v\n", name, present)
    } else {
        fmt.Printf("%s not found in attendance\n", name)
    }

    name = "Priya"
    if present, ok := attendance[name]; ok {
        fmt.Printf("%s is marked present: %v\n", name, present)
    } else {
        fmt.Printf("%s not found in attendance\n", name)
    }
}

When executed, this program outputs:

Rohit is marked present: true
Priya not found in attendance

Check Before Accessing Value

It’s a good practice to check for existence before using the value, especially when zero values are meaningful.

Example

This example shows how to handle such a case with student marks:

package main
import "fmt"

func main() {
    marks := map[string]int{
        "Amit": 78,
        "Neha": 92,
    }

    name := "Neha"
    if score, exists := marks[name]; exists {
        fmt.Printf("Marks of %s: %d\n", name, score)
    } else {
        fmt.Printf("No record found for %s\n", name)
    }

    name = "Kunal"
    if score, exists := marks[name]; exists {
        fmt.Printf("Marks of %s: %d\n", name, score)
    } else {
        fmt.Printf("No record found for %s\n", name)
    }
}

When executed, this program outputs:

Marks of Neha: 92
No record found for Kunal

Why Use the Comma-ok Idiom?

If your map's value type has a default zero value (like 0 for int or "" for string), accessing a non-existing key may return the zero value, making it hard to distinguish from an actual entry with that value. The comma-ok idiom solves this by confirming the presence of the key.

Example

package main
import "fmt"

func main() {
    balance := map[string]int{
        "Delhi":    0,
        "Mumbai":   200,
    }

    city := "Delhi"
    value, ok := balance[city]
    if ok {
        fmt.Printf("%s has a balance of ₹%d\n", city, value)
    } else {
        fmt.Printf("%s not found in balance records\n", city)
    }

    city = "Chennai"
    value, ok = balance[city]
    if ok {
        fmt.Printf("%s has a balance of ₹%d\n", city, value)
    } else {
        fmt.Printf("%s not found in balance records\n", city)
    }
}

When executed, this program outputs:

Delhi has a balance of ₹0
Chennai not found in balance records

Exercise

Select the correct answer for each question about checking for specific elements in Go maps.

1. What does the second value in a map lookup represent? --Select-- Whether the key exists The key name The map's size
2. How would you check if a key exists in a map? --Select-- value, ok := map[key] map.exists(key) check(map, key)
3. What is returned when a key is not found in the map? --Select-- Zero value and false nil and true Panic error