TypeError: object of type 'int' has no len()

What this error means

len() only works on things that contain items — strings, lists, tuples, dicts, sets, ranges. A number contains nothing, so it has no length and Python says so. The message names the actual type, so the same bug reads 'float' object has no len(), 'bool' object has no len() or 'NoneType' object has no len().

Traceback (most recent call last):
  File "demo.py", line 3, in <module>
    print(len(total))
          ^^^^^^^^^^
TypeError: object of type 'int' has no len()

Cause 1 — counting the digits of a number

The intent is usually 'how many digits does this number have?' That is a real question, but len() cannot answer it directly — convert to a string first, or use arithmetic:

total = 4821

len(total)                     # TypeError
len(str(total))                # 4  — the simple, readable fix
len(str(abs(total)))           # 4  — ignores the minus sign

digits = 0                     # arithmetic version, no conversion
n = abs(total)
while n:
    n //= 10
    digits += 1

Cause 2 — a variable that changed type

Very often the variable was a list and something reassigned it to a number. The len() line is correct; the mistake is upstream:

scores = [90, 85, 72]
print(len(scores))     # 3 — fine

scores = sum(scores)   # scores is now the number 247
print(len(scores))     # TypeError

Cause 3 — a function returned a count instead of a collection

A function named get_items that returns len(items), or a database call that returns a row count, leaves the caller holding an integer:

def active_users(rows):
    return len([r for r in rows if r["active"]])   # returns a number

users = active_users(data)
if len(users) > 0:      # TypeError — users is already a count
    ...

if users > 0:           # what was meant

Cause 4 — len() on a generator or a single value

Generators, iterators, map, filter, zip and enumerate objects are not sized, so len() refuses them too. Materialise them first:

squares = (n * n for n in range(5))
len(squares)                 # TypeError: object of type 'generator' has no len()

squares = list(squares)      # or [n * n for n in range(5)]
len(squares)                 # 5

How to debug it

1. Print type(value) right before the len(). The message already told you the type — this confirms where it came from.
2. Search backwards for an assignment to that name. A reassignment from a collection to a number is the most common story.
3. If you wanted the digit count, use len(str(abs(n))).
4. If the value came from a function, read what it returns on every path — a count and a collection are easy to confuse when both are named total or result.
5. If it is a generator or iterator, wrap it in list() — but only if you actually need the length; otherwise iterate it and count as you go.

Fix it interactively

These free problems practice the length and type rules — repair them in the browser:

• Wrong function to find list length easy

Related messages worth knowing

• 'int' object is not iterable — the same number, met by a for loop instead of len().
• 'int' object is not subscriptable — the same number, met by square brackets.
• 'int' object is not callable — the same number, met by parentheses.