 # Indexing array thorough another array

happy new year
my name is frank, I try to display an array thorough another array but I get error message

``````#import numpy as np
listOfNum1 = [23, 45, 21, 45, 2, 5, 11, 50, 1, 67]
listOfNum2 = [23, 45, 21, 45, 2, 5, 11, 50, 1, 67]
index1 = [1,2,3,4,5,6,7,8,9,10]
index2 = [1,2,3,4,5,6,7,8,9,10]
#arr = np.array([1,2,3,4,5,6,7,8,9,10])
#arrlist1 = np.array([23, 45, 21, 45, 2, 5, 11, 50, 1, 67])
a=0
b=0
sorted(range(len(listOfNum1)), key=lambda k: listOfNum1[k])
print("Elements in the list are : ")
for i in range(len(listOfNum1)):
print("Element",i," in the list are : ",(listOfNum1[i]))
print("Elements in the list are : ")
for j in range(len(listOfNum1)):
for k in range(len(listOfNum1)-1):
if listOfNum1[k]<listOfNum1[k+1]:
#a=listOfNum1[k]
#listOfNum1[k] = listOfNum1[k+1]
#listOfNum1[k+1]=a
#a=0
a=listOfNum1[k]
listOfNum1[k] = listOfNum1[k+1]
listOfNum1[k+1]=a
a=0
b=index1[k]
index1[k]=index1[k+1]
index1[k+1]=b
b=0
#print("Element",j," in the list are : ",index1[j],listOfNum1[j])
print("Elements in the list are : ")
for j in range(len(listOfNum1)):
b=index1[j]
print("Element",j," in the list are : ",index1[j],listOfNum1[j])

print("Elements in the list are : ")
for j in range(len(listOfNum2)):
b=index1[j]
print("Element",j," in the list are : ",b,listOfNum2[b])

``````

Hello @toronto2009.
Welcome to FCC.
When I run your code on repl.it, I get the following error.

``````Traceback (most recent call last):
File "main.py", line 40, in <module>
print("Element",j," in the list are : ",b,listOfNum2[b])
IndexError: list index out of range
``````

The error is in the last `for` loop. Try adding the following lines of code just before the last `for` loop.

``````print(listOfNum2)
print(index1)
``````

Essentially the values of `b` are the elements of `index1` array and you are trying to access `listOfNum2[b])` yet some elements of `index1` are greater than the index of the last element of `listOfNum2`. As a result you get the above error. I hope that helps.