Getting an NameError but my variable is defined

Question

I do not know why I am getting this error

NameError: name 'len_num' is not defined

def is_armstrong_number(num):
#Convert number to string
    num_str = str(num)
#Get length of number
    len_num = len(num_str)
#Select each number in string and store it in list
for x in range(1,len_num):
    num_list.insert(x,num_str[x])
#Convert back to int
    int(num_list)
#Compare armstrong number and list
for x in range(1,len_num):
   if num == num_list(x) ** len_num:
    print("It is an armstrong number")
else: print("It is not an armstrong number")
pass  

len_num is local to the function so I do not see the issue with the name since it is defined before it is used.

Answer 1

Your issues could be with identation. Compare with my code:

def is_armstrong_number(num):
    #Convert number to string
    num_str = str(num)
    #Get length of number
    len_num = len(num_str)
    #Select each number in string and store it in list
    for x in range(1,len_num):
        num_list.insert(x,num_str[x])
    #Convert back to int
        int(num_list)
    #Compare armstrong number and list
    for x in range(1,len_num):
       if num == num_list(x) ** len_num:
        print("It is an armstrong number")
    else: print("It is not an armstrong number")
    pass

is_armstrong_number(2)
# Output
# It is not an armstrong number
~                      

I don't get the error after running.