Why do I get "TypeError: 'int' object is not iterable" when trying to sum digits of a number?

Question

Here's my code:

import math

print("Hey, lets solve Task 4 :)")

number1 = input("How many digits do you want to look at? ")
number2 = input("What would you like the digits to add up to? ")

if number1 == 1:
    cow = range(0,10)
elif number1 == 2:
    cow = range(10,100)
elif number1 == 3:
    cow = range(100,1000)
elif number1 == 4:
    cow = range(1000,10000)
elif number1 == 5:
    cow = range(10000,100000)
elif number1 == 6:
    cow = range(100000,1000000)
elif number1 == 7:
    cow = range(1000000,10000000)
elif number1 == 8:
    cow = range(10000000,100000000)
elif number1 == 9:
    cow = range(100000000,1000000000)
elif number1 == 10:
    cow = range(1000000000,10000000000)

number3 = cow[-1] + 1

n = 0
while n < number3:
    number4 = list(cow[n])
    n += 1

I am looking to make a loop so that for each element in the list, it will get broken down into each of it's characters. For example, say the number 137 was in the list then it would be turned into [1,3,7]. Then I want to add these numbers together (I haven't started that bit yet but I have some idea of how to do it).

However, I keep getting this error message:

TypeError: 'int' object is not iterable

What am I doing wrong?

Answer 1

Your problem is with this line:

number4 = list(cow[n])

It tries to take cow[n], which returns an integer, and make it a list. This doesn't work, as demonstrated below:

>>> a = 1
>>> list(a)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
>>>

Perhaps you meant to put cow[n] inside a list:

number4 = [cow[n]]

See a demonstration below:

>>> a = 1
>>> [a]
[1]
>>>

---

Also, I wanted to address two things:

1. Your while-statement is missing a : at the end.
2. It is considered very dangerous to use input like that, since it evaluates its input as real Python code. It would be better here to use raw_input and then convert the input to an integer with int.

---

To split up the digits and then add them like you want, I would first make the number a string. Then, since strings are iterable, you can use sum:

>>> a = 137
>>> a = str(a)
>>> # This way is more common and preferred
>>> sum(int(x) for x in a)
11
>>> # But this also works
>>> sum(map(int, a))
11
>>>