Go Maps
Key-value pairs for efficient data storage in Go
🗺️ What are Go Maps?
Maps are Go's built-in associative data type that store key-value pairs. They provide fast lookups, additions, and deletions based on keys, similar to dictionaries or hash tables.
// Create and use a map
ages := map[string]int{"Alice": 25, "Bob": 30}
ages["Charlie"] = 35
fmt.Println(ages["Alice"]) // Output: 25
Output:
25
Key Map Concepts
Key-Value Pairs
Store data as key-value associations
scores := map[string]int{
"Math": 95,
"Science": 87
}Fast Lookup
Quick access to values using keys
mathScore := scores["Math"] // O(1) lookupDynamic
Add, update, and delete entries anytime
scores["History"] = 92 // Add
delete(scores, "Math") // DeleteUnique Keys
Each key can appear only once
// Keys must be unique
// Values can be duplicated🔹 Creating Maps
Several ways to create and initialize maps in Go:
package main
import "fmt"
func main() {
// Method 1: Map literal
colors := map[string]string{
"red": "#FF0000",
"green": "#00FF00",
"blue": "#0000FF",
}
// Method 2: Make function
ages := make(map[string]int)
ages["Alice"] = 25
ages["Bob"] = 30
// Method 3: Empty map literal
var scores map[string]int
scores = map[string]int{}
scores["Math"] = 95
// Method 4: Make with initial capacity
inventory := make(map[string]int, 10)
inventory["apples"] = 50
fmt.Println("Colors:", colors)
fmt.Println("Ages:", ages)
fmt.Println("Scores:", scores)
fmt.Println("Inventory:", inventory)
}Output:
Colors: map[blue:#0000FF green:#00FF00 red:#FF0000]
Ages: map[Alice:25 Bob:30]
Scores: map[Math:95]
Inventory: map[apples:50]
🔹 Map Operations
Common operations for working with maps:
package main
import "fmt"
func main() {
// Create a map
students := map[string]int{
"Alice": 85,
"Bob": 92,
"Charlie": 78,
}
// Access values
fmt.Println("Alice's score:", students["Alice"])
// Add new entry
students["Diana"] = 96
fmt.Println("After adding Diana:", students)
// Update existing entry
students["Bob"] = 95
fmt.Println("After updating Bob:", students)
// Check if key exists
score, exists := students["Eve"]
if exists {
fmt.Println("Eve's score:", score)
} else {
fmt.Println("Eve not found")
}
// Delete entry
delete(students, "Charlie")
fmt.Println("After deleting Charlie:", students)
// Get map length
fmt.Println("Number of students:", len(students))
}Output:
Alice's score: 85
After adding Diana: map[Alice:85 Bob:92 Charlie:78 Diana:96]
After updating Bob: map[Alice:85 Bob:95 Charlie:78 Diana:96]
Eve not found
After deleting Charlie: map[Alice:85 Bob:95 Diana:96]
Number of students: 3
🔹 Iterating Over Maps
Use range loops to iterate through map entries:
package main
import "fmt"
func main() {
prices := map[string]float64{
"apple": 1.20,
"banana": 0.80,
"orange": 1.50,
"grape": 2.00,
}
// Method 1: Iterate over key-value pairs
fmt.Println("All items and prices:")
for item, price := range prices {
fmt.Printf("%s: $%.2f\n", item, price)
}
// Method 2: Iterate over keys only
fmt.Println("\nAll items:")
for item := range prices {
fmt.Println("-", item)
}
// Method 3: Iterate over values only
fmt.Println("\nAll prices:")
for _, price := range prices {
fmt.Printf("$%.2f ", price)
}
fmt.Println()
// Calculate total
total := 0.0
for _, price := range prices {
total += price
}
fmt.Printf("\nTotal value: $%.2f\n", total)
}Output:
All items and prices:
apple: $1.20
banana: $0.80
orange: $1.50
grape: $2.00
All items:
- apple
- banana
- orange
- grape
All prices:
$1.20 $0.80 $1.50 $2.00
Total value: $5.50