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Situation:
I've a slice of values and need to pick up a randomly chosen value from it. Then I want to concatenate it with a fixed string. This is my code so far:
func main() { //create the reasons slice and append reasons to it reasons := make([]string, 0) reasons = append(reasons, "Locked out", "Pipes broke", "Food poisoning", "Not feeling well") message := fmt.Sprint("Gonna work from home...", pick a random reason ) } Question:
Is there a built-in function, which can help me by doing the "pick a random reason" part?
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Golang has built-in support for random number generation in the standard library. Specifically there is the math/rand package which implements pseudo-random number generators. Intn returns, as an int, a non-negative pseudo-random number in [0,n) from the default Source.
Use the random. sample() function when you want to choose multiple random items from a list without repetition or duplicates. There is a difference between choice() and choices() . The choices() was added in Python 3.6 to choose n elements from the list randomly, but this function can repeat items.
The most naive approach is to randomly pick an item from your existing slice, remove it, and then insert it into a new slice. We can use the math/rand package’s Intn () method to pick the random element, and we can use append to remove elements from the middle of our slice.
Random element from slice To generate a character from an arbitrary set, choose a random index from a slice of characters: chars := []rune("AB⌘") c := chars[rand.Intn(len(chars))] // for example '⌘'
The Go playground uses a fixed time so you will always get the same slice returned. Run it locally to see random shuffles. Intn (N) works by generating a random number between 0 and N (but not N) and then returning it. We can use this to pick a random element by using it to select a valid index and then getting the element at that index.
We pick a random letter by generating a random index of the string. We run the example three times. Go provides cryptographically secure pseudorandom number generator in the standard library package crypto/rand. While math/random is much faster, crypto/rand is suited for programs where security is paramount.
Use function Intn from rand package to select a random index.
import ( "math/rand" "time" ) // ... rand.Seed(time.Now().Unix()) // initialize global pseudo random generator message := fmt.Sprint("Gonna work from home...", reasons[rand.Intn(len(reasons))]) Other solution is to use Rand object.
s := rand.NewSource(time.Now().Unix()) r := rand.New(s) // initialize local pseudorandom generator r.Intn(len(reasons)) Just pick a random integer mod slice length:
rand.Seed(time.Now().Unix()) reasons := []string{ "Locked out", "Pipes broke", "Food poisoning", "Not feeling well", } n := rand.Int() % len(reasons) fmt.Print("Gonna work from home...", reasons[n]) Playground: http://play.golang.org/p/fEHElLJrEZ. (Note the commend about rand.Seed.)
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