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TypeError: 'int' object is not iterable

What it means

Python expected something it could go through one item at a time, such as a list, a string or a range, and got a single number. A for loop, sum(), max() and list() all need a collection, not one number.

1. Looping over a number instead of a range

This raises the error

Broken
times = 3
for i in times:
print("Hello", i)
Output
Traceback (most recent call last):
  File "<exec>", line 2, in <module>
TypeError: 'int' object is not iterable

The fix

Fixed
times = 3
for i in range(times):
print("Hello", i)
Output
Hello 0
Hello 1
Hello 2

range(3) gives the numbers 0, 1 and 2, so the loop runs 3 times. The number 3 on its own has nothing to loop over.

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2. Looping over `len()` of a list

This raises the error

Broken
names = ["Ada", "Alan", "Grace"]
for i in len(names):
print(i, names[i])
Output
Traceback (most recent call last):
  File "<exec>", line 2, in <module>
TypeError: 'int' object is not iterable

The fix

Fixed
names = ["Ada", "Alan", "Grace"]
for i, name in enumerate(names):
print(i, name)
Output
0 Ada
1 Alan
2 Grace

len(names) is the single number 3. enumerate() gives each position together with its item. range(len(names)) also works.

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3. Adding up the digits of a number with `sum()`

This raises the error

Broken
n = 1234
print(sum(n))
Output
Traceback (most recent call last):
  File "<exec>", line 2, in <module>
TypeError: 'int' object is not iterable

The fix

Fixed
n = 1234
print(sum(int(d) for d in str(n)))
Output
10

A number has no digits to loop over, but its string does. Each character goes back to a number with int() before adding.

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When you see this error, check

  • To repeat something n times, loop over range(n).
  • Loop over the list itself, or enumerate(list), instead of len(list).
  • Print the value and its type() just before the loop.
  • For digits, turn the number into a string first: str(n).

Related errors

All Python errors · How to read a traceback · Step through your code