Go by Example: Maps

Maps are Go’s built-in associative data type (sometimes called hashes or dicts in other languages).
	package main
	import "fmt"
	func main() {
To create an empty map, use the builtin `make`: `make(map[key-type]val-type)`.	m := make(map[string]int)
Set key/value pairs using typical `name[key] = val` syntax.	m["k1"] = 7 m["k2"] = 13
Printing a map with e.g. `fmt.Println` will show all of its key/value pairs.	fmt.Println("map:", m)
Get a value for a key with `name[key]`.	v1 := m["k1"] fmt.Println("v1:", v1)
If the key doesn’t exist, the zero value of the value type is returned.	v3 := m["k3"] fmt.Println("v3:", v3)
The builtin `len` returns the number of key/value pairs when called on a map.	fmt.Println("len:", len(m))
The builtin `delete` removes key/value pairs from a map.	delete(m, "k2") fmt.Println("map:", m)
To remove all key/value pairs from a map, use the `clear` builtin.	clear(m) fmt.Println("map:", m)
The optional second return value when getting a value from a map indicates if the key was present in the map. This can be used to disambiguate between missing keys and keys with zero values like `0` or `""`. Here we didn’t need the value itself, so we ignored it with the blank identifier `_`.	_, prs := m["k2"] fmt.Println("prs:", prs)
You can also declare and initialize a new map in the same line with this syntax.	n := map[string]int{"foo": 1, "bar": 2} fmt.Println("map:", n) }

Note that maps appear in the form map[k:v k:v] when printed with fmt.Println.

$ go run maps.go 
map: map[k1:7 k2:13]
v1: 7
v3: 0
len: 2
map: map[k1:7]
map: map[]
prs: false
map: map[bar:2 foo:1]

Next example: Range.