import numpy as np
import time as tm

odd = np.array([])
value = 0
t = tm.time()

for i in range(0, 100000, 1):
    value = 2*i+1
    odd = np.append(odd, value)
   
elapsed1 = tm.time() - t
print('Without preallocation:', elapsed1)

odd = np.zeros([100000])
value = 0
t = tm.time()

for i in range(0, 100000, 1):
    value = 2*i+1
    odd[i] = value 

elapsed2 = tm.time() - t
print('With preallocation:', elapsed2)