CODEWITHSUNDEEP
pythonnumpyrandomrange
bgarrood
bgarrood

Reputation: 487

Python generate range array with random step size

Goals: to Initialize an array with pre-defined size with a random number. I have try this way and working:

xa = np.empty(100)
xa[0] = random.random()
for i in range(1,100):
    xa[i] = xa[i-1] + random.random()

My question: Is there any better way to do it? maybe without the for loop?

Upvotes: 2

Views: 5561

Answers (5)

Dani Mesejo
Dani Mesejo

Reputation: 61910

Given that you are using numpy the code in your question is equivalent to:

import numpy as np
np.random.seed(42)

xa = np.cumsum(np.random.random(100))
print(xa[:5])

Output

[0.37454012 1.32525443 2.05724837 2.65590685 2.81192549]

But if what you want if something that returns a range (like the one from the range function), but with a random step you could do something like this:

xa = np.cumsum(np.random.randint(100, size=(100,)))
print(xa[:5])

Output

[ 62 157 208 303 306]

Note that in both cases only the first 5 numbers are printed. Also in both cases the step is positive.

Further

  1. Documentation on cumsum, randint and random.

Upvotes: 1

r.ook
r.ook

Reputation: 13858

Use list comprehension:

import random
n = 100   # your array size
xa = [random.random() for _ in range(n)]

Again as mentioned, np.empty(100) would already give you a fully random array of the size. What is the issue with np.empty()?

Upvotes: 0

Geo Joy
Geo Joy

Reputation: 357

Simple one-liner

import random 
xa = random.sample(range(1, 101), 100)

Upvotes: 2

vishes_shell
vishes_shell

Reputation: 23484

You also can use itertools.accumulate function:

from itertools import accumulate
import numpy as np
import random

xa = np.empty(100)
xa[0] = random.random()

xa = list(accumulate(xa, lambda x, y: x + random.random()))

I am not quite sure that this is what you need, but it computes every element with prev + random.random() like you wrote in your question.

Upvotes: 1

AhmedHaies
AhmedHaies

Reputation: 90

you can use this better than your code

import random
xa = [None] * 100
xa[0] = random.random()
for i in xrange(1, 100):
        xa[i] = xa[i-1] + random.random()

Upvotes: 0

Related Questions