How to repeat the numbers in a list in python?

You can perform this operation using numpy without using a for loop.

np.repeat(a, repeats) will repeat the input array a according to repeats which specify the number of repetitions for each element.

import numpy as np
A = [1,6,3,8,5,5,2,1,2,10]
B = np.repeat(A,A)

Output:

>>> array([ 1,  6,  6,  6,  6,  6,  6,  3,  3,  3,  8,  8,  8,  8,  8,  8,  8,
    8,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  2,  2,  1,  2,  2, 10,
   10, 10, 10, 10, 10, 10, 10, 10, 10])

Using the repeat function of NumPy you can get the solution

import numpy as np
np.repeat(A, A)

You should use nested loop

l  = [1, 6, 3]
nl = []
for number in l:
    for i in range(number):
        nl.append(number)
print(nl)

or using list comprehension

l = [1,6,3]
nl = [number  for number in l for i in range(number)]
#[1, 6, 6, 6, 6, 6, 6, 3, 3, 3] 

hello you can make this with the lib itertools:

import itertools
lst = [1,2,3,4,5]
# [1, 2, 3, 4, 5]
list(itertools.chain.from_iterable(itertools.repeat(x, x) for x in lst)) 
#[1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5]

You have a list of integers, to which the multiplication means arithmetic multiplication. You need to convert them into strings.

A = [1,6,3,8,5,5,2,1,2,10]
new_A = [x * str(x) for x in A]

which is called list comprehension, being a much cleaner/pythonic way of:

for x in A:
new_A.append(x * str(x))

B = np.concatenate([[a]*a for a in A])

>>> array([ 1,  6,  6,  6,  6,  6,  6,  3,  3,  3,  8,  8,  8,  8,  8,  8,  8,
    8,  5,  5,  5,  5,  5,  5,  5,  5,  5,  5,  2,  2,  1,  2,  2, 10,
   10, 10, 10, 10, 10, 10, 10, 10, 10])

nums = [1, 5, 4]
res = []
for num in nums:
    res.extend([num] * num)
print(res)
# [1, 5, 5, 5, 5, 5, 4, 4, 4, 4]