i want to fill an array which his length is 20 with randomly number from 1 to 100 in python

Question

i want to fill an array which his length is 20 with randomly number from 1 to 100 in python

import numpy as np
a = np.empty(shape=5)
print(a)
for i in range(50){
    a[i]=randint(1,100);}

Answer 1

You can both create an array or fill an array with 20 random integers using numpy.random.randint():

import numpy as np

# create an 20-element array of random integres in [1, 100]
a = np.random.randint(1, 101, size = 20)
print(a)

# create an uninitialized array of 20 integers 
b = np.empty(20, dtype = int)
# fill b with 20 random integers in [1, 100]
for i in range(len(b)):
    b[i] = np.random.randint(1, 101, size = 1)
print(b)

Sample Output:

# array a
[56 39 20 14 78 58 86 72 67 87 79 78 84 49 43 80 79 21 46 31]
# array b
[50 26 87 22  6 37 36 32 84 79 62  2 79 45 90 66 67 30 26 85]

In my code above:

• numpy.random.randint(1, 101, size = 20) (documentation) creates a 20-element array of random integers in the closed interval [1, 100];
• numpy.random.randint(1, 101, size = 1) creates a scalar array (1-element) of a random integer in the closed interval [1, 100]. We generate 20 such random integers and assign each of them to a different element of the array b of integers.

Notes regarding your code:

• a = np.empty(shape=5) (documentation) creates an uninitialized array of 5 floats; if you need 20 elements, this should be 20;
• if you need an array of integers, you should specify this using the dtype optional argument as I have done above. If you do not specify dtype, by default, you will be allocated an uninitialized array of floats.