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_Maps_ are Go's built-in [associative data type](http://en.wikipedia.org/wiki/Associative_array) (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)

    
map: map[k1:7 k2:13]







    
    
        
    

    






    
    
         Get a value for a key with `name[key]`.
    
	v1 := m["k1"]

    






    
    
	fmt.Println("v1: ", v1)

    
v1:  7







    
    
        
    

    






    
    
         The builtin `len` returns the number of key/value pairs when called on a map.
    
	fmt.Println("len:", len(m))

    
len: 2







    
    
        
    

    






    
    
         The builtin `delete` removes key/value pairs from a map.
    
	delete(m, "k2")

    






    
    
	fmt.Println("map:", m)

    
map: map[k1:7]







    
    
        
    

    






    
    
         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)

    
prs: false







    
    
        
    

    






    
    
         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)

    
map: map[bar:2 foo:1]







    
    
}

    






    
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