CODEWITHSUNDEEP
pythonlistrandom
Linda Leang
Linda Leang

Reputation: 717

Python: Random numbers into a list

Create a 'list' called my_randoms of 10 random numbers between 0 and 100.

This is what I have so far:

import random
my_randoms=[]
for i in range (10):
    my_randoms.append(random.randrange(1, 101, 1))
    print (my_randoms)

Unfortunately Python's output is this:

[34]
[34, 30]
[34, 30, 75]
[34, 30, 75, 27]
[34, 30, 75, 27, 8]
[34, 30, 75, 27, 8, 58]
[34, 30, 75, 27, 8, 58, 10]
[34, 30, 75, 27, 8, 58, 10, 1]
[34, 30, 75, 27, 8, 58, 10, 1, 59]
[34, 30, 75, 27, 8, 58, 10, 1, 59, 25]

It generates the 10 numbers like I ask it to, but it generates it one at a time. What am I doing wrong?

Upvotes: 68

Views: 242409

Answers (10)

karthikr
karthikr

Reputation: 99620

Fix the indentation of the print statement:

import random

my_randoms=[]
for i in range (10):
    my_randoms.append(random.randrange(1,101,1))

print (my_randoms)

This works because you are printing my_randoms each time one of the values is generated. By unindenting the print() statement, it is placed outside the loop and only executed once after the for loop has finished.

Upvotes: 19

user7864386
user7864386

Reputation:

The one random list generator in the random module not mentioned here is random.choices:

my_randoms = random.choices(range(0, 100), k=10)

It's like random.sample but with replacement. The sequence passed doesn't have to be a range; it doesn't even have to be numbers. The following works just as well:

my_randoms = random.choices(['a','b'], k=10)

If we compare the runtimes, among random list generators, random.choices is the fastest no matter the size of the list to be created. However, for larger lists/arrays, numpy options are much faster. So for example, if you're creating a random list/array to assign to a pandas DataFrame column, then using np.random.randint is the fastest option.

enter image description here

Code used to produce the above plot:

import perfplot
import numpy as np
import random

perfplot.show(
    setup=lambda n: n,
    kernels=[
        lambda n: [random.randint(0, n*2) for x in range(n)],
        lambda n: random.sample(range(0, n*2), k=n), 
        lambda n: [random.randrange(n*2) for i in range(n)],
        lambda n: random.choices(range(0, n*2), k=n), 
        lambda n: np.random.rand(n), 
        lambda n: np.random.randint(0, n*2, size=n),
        lambda n: np.random.choice(np.arange(n*2), size=n),
    ],
    labels=['random_randint', 'random_sample', 'random_randrange', 'random_choices', 
            'np_random_rand', 'np_random_randint', 'np_random_choice'],
    n_range=[2 ** k for k in range(17)],
    equality_check=None,
    xlabel='~n'
)

Upvotes: 0

Pobaranchuk
Pobaranchuk

Reputation: 877

Simple solution:

indices=[]
for i in range(0,10):
  n = random.randint(0,99)
  indices.append(n)

Upvotes: 0

robertklep
robertklep

Reputation: 203241

You could use random.sample to generate the list with one call:

import random
my_randoms = random.sample(range(100), 10)

That generates numbers in the (inclusive) range from 0 to 99. If you want 1 to 100, you could use this (thanks to @martineau for pointing out my convoluted solution):

my_randoms = random.sample(range(1, 101), 10)

Upvotes: 97

vestland
vestland

Reputation: 61074

xrange() will not work for 3.x.

numpy.random.randint().tolist() is a great alternative for integers in a specified interval:

 #[In]:
import numpy as np
np.random.seed(123) #option for reproducibility
np.random.randint(low=0, high=100, size=10).tolist()

#[Out:]

[66, 92, 98, 17, 83, 57, 86, 97, 96, 47]

You also have np.random.uniform() for floats:

#[In]:
np.random.uniform(low=0, high=100, size=10).tolist()

#[Out]:
[69.64691855978616,
28.613933495037948,
22.68514535642031,
55.13147690828912,
71.94689697855631,
42.3106460124461,
98.07641983846155,
68.48297385848633,
48.09319014843609,
39.211751819415056]

Upvotes: 4

Ben Solien
Ben Solien

Reputation: 151

This is way late but in-case someone finds this helpful.

You could use list comprehension.

rand = [random.randint(0, 100) for x in range(1, 11)]
print(rand)

Output:

[974, 440, 305, 102, 822, 128, 205, 362, 948, 751]

Cheers!

Upvotes: 13

Stryker
Stryker

Reputation: 6120

Here I use the sample method to generate 10 random numbers between 0 and 100.

Note: I'm using Python 3's range function (not xrange).

import random

print(random.sample(range(0, 100), 10))

The output is placed into a list:

[11, 72, 64, 65, 16, 94, 29, 79, 76, 27]

Upvotes: 8

mattexx
mattexx

Reputation: 6606

import random
my_randoms = [random.randrange(1, 101, 1) for _ in range(10)]

Upvotes: 53

someguy
someguy

Reputation: 1

my_randoms = [randint(n1,n2) for x in range(listsize)]

Upvotes: -3

perwaiz alam
perwaiz alam

Reputation: 11

import random

a=[]
n=int(input("Enter number of elements:"))

for j in range(n):
       a.append(random.randint(1,20))

print('Randomised list is: ',a)

Upvotes: 1

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