rand package in Golang

Go language provides inbuilt support for generating random numbers of the specified type with the help of a math/rand package. This package implements pseudo-random number generators. These random numbers are generated by a source and this source produces a deterministic sequence of values every time when the program run. And if you want to random numbers for security-sensitive work, then use the crypto/rand package.

Note: In this package, the mathematical interval notation such as [0, n) is used.

Function	Description
ExpFloat64	This function returns an exponentially distributed float64 in the range (0, +math.MaxFloat64] with an exponential distribution from the default source.
Float32	This function returns, as a float32, a pseudo-random number in [0.0, 1.0) from the default source.
Float64	This function returns, as a float64, a pseudo-random number in [0.0, 1.0) from the default source.
Int	This function returns a non-negative pseudo-random int from the default source.
Int31	This function returns a non-negative pseudo-random 31-bit integer as an int32 from the default source.
Int31n	This function returns, as an int32, a non-negative pseudo-random number in [0, n) from the default source.
Int63	This function returns a non-negative pseudo-random 63-bit integer as an int64 from the default source.
Int63n	This function returns, as an int64, a non-negative pseudo-random number in [0, n) from the default source.
Intn	This function returns, as an int, a non-negative pseudo-random number in [0, n) from the default source.
NormFloat64	This function returns a normally distributed float64 in the range [-math.MaxFloat64, +math.MaxFloat64] with standard normal distribution (mean = 0, stddev = 1) from the default source.
Perm	This function returns, as a slice of n ints, a pseudo-random permutation of the integers [0, n) from the default source.
Read	This function generates len(p) random bytes from the default source and writes them into p.
Seed	This function provided seed value to initialize the default source to a deterministic state and if Seed is not called, the generator behaves as if seeded by Seed(1)..
Shuffle	This function pseudo-randomizes the order of elements using the default source.
Uint32	This function returns a pseudo-random 32-bit value as a uint32 from the default source.
Uint64	This function returns a pseudo-random 64-bit value as a uint64 from the default source.

type Rand

Method	Description
func New	This function returns a new Rand that uses random values from src to generate other random values.
func (*Rand) ExpFloat64	This method is used to return an exponentially distributed float64 in the range (0, +math.MaxFloat64] with an exponential distribution.
func (*Rand) Float32	This method returns, as a float32, a pseudo-random number in [0.0, 1.0).
func (*Rand) Float64	This method returns, as a float64, a pseudo-random number in [0.0, 1.0).
func (*Rand) Int	This method returns a non-negative pseudo-random int.
func (*Rand) Int31	This method returns a non-negative pseudo-random 31-bit integer as an int32.
func (*Rand) Int31n	This method returns, as an int32, a non-negative pseudo-random number in [0, n).
func (*Rand) Int63	This method returns a non-negative pseudo-random 63-bit integer as an int64.
func (*Rand) Int63n	This method returns, as an int64, a non-negative pseudo-random number in [0, n).
func (*Rand) Intn	This method returns, as an int, a non-negative pseudo-random number in [0, n).
func (*Rand) NormFloat64	This method is used to return a normally distributed float64 in the range -math.MaxFloat64 through +math.MaxFloat64 inclusive, with standard normal distribution (mean = 0, stddev = 1).
func (*Rand) Perm	This method returns, as a slice of n ints, a pseudo-random permutation of the integers [0, n).
func (*Rand) Read	This method generates len(p) random bytes and writes them into p.
func (*Rand) Seed	This method provided seed value to initialize the generator to a deterministic state.
func (*Rand) Shuffle	This method pseudo-randomizes the order of elements.
func (*Rand) Uint32	This method returns a pseudo-random 32-bit value as a uint32.
func (*Rand) Uint64	This method returns a pseudo-random 64-bit value as a uint64.

type Source

Method	Description
func NewSource	This function returns a new pseudo-random Source seeded with the given value.
type Source64	It is a Source that can also generate uniformly-distributed pseudo-random uint64 values in the range [0, 1<<64) directly. If a Rand r's underlying Source s implements Source64, then r.Uint64 returns the result of one call to s.Uint64 instead of making two calls to s.Int63.

type Zipf

Method	Description
func NewZipf	This function returns a Zipf variate generator.
func (*Zipf) Uint64	This method returns a value drawn from the Zipf distribution described by the Zipf object.

Example 1:

// Golang program to illustrate
// how to Get Intn Type Random
// Number
package main

import (
    "fmt"
    "math/rand"
)

// Main function
func main() {

    // Finding random numbers of int type
    // Using Intn() function
    res_1 := rand.Intn(7)
    res_2 := rand.Intn(8)
    res_3 := rand.Intn(2)

    // Displaying the result
    fmt.Println("Random Number 1: ", res_1)
    fmt.Println("Random Number 2: ", res_2)
    fmt.Println("Random Number 3: ", res_3)
}

Output:

Random Number 1:  6
Random Number 2:  7
Random Number 3:  1

Example 2:

// Golang program to illustrate
// how to get a random number
package main

import (
    "fmt"
    "math/rand"
)

// Main function
func main() {

    // Finding random numbers of int type
    // Using Int31() function
    res_1 := rand.Int31()
    res_2 := rand.Int31()
    res_3 := rand.Int31()

    // Displaying the result
    fmt.Println("Random Number 1: ", res_1)
    fmt.Println("Random Number 2: ", res_2)
    fmt.Println("Random Number 3: ", res_3)
}

Output:

Random Number 1:  1298498081
Random Number 2:  2019727887
Random Number 3:  1427131847