TypeError: 'int' object is not callable

TypeError: 'int' object is not callable means the code put parentheses after a value that is a number. Python only lets you call functions, classes and other callable objects, so 5(...) fails. The most common cause is a variable that shadows a built-in: after sum = 10, the name sum no longer refers to the built-in function, and the next sum(items) tries to call the integer 10.

Reproduce it

python3 - <<'PY'
sum = 10
print(sum([1, 2, 3]))
PY

Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
TypeError: 'int' object is not callable

The traceback names the line with the call and ends with the type of the object that was called. The type in quotes changes with the value: 'int', 'str', 'float', 'list' or 'dict'. Everything below applies to all of them.

Cause 1: a variable shadows a built-in

Python looks up a name in the local scope first, then the enclosing scopes, the module and finally the built-ins. An assignment creates a name in the current scope, so it hides the built-in with the same name for the rest of that scope. Typical victims are sum, max, min, len, int, id, input, list, dict, str and type. Counters and accumulators are the usual way it happens.

Recognise it: the failing line calls a well-known built-in, and an earlier line in the same file assigns a number to that name.

python3 - <<'PY'
import builtins
total = 10
print(sum([1, 2, 3]))
print(callable(builtins.sum), callable(total))
PY

6
True False

Renaming the variable fixes it, and callable() tells you at a glance whether a name can be called.

Cause 2: a missing operator

Mathematical notation allows 2(3 + 4). Python does not insert a multiplication sign, it reads the expression as a call of 2. Python 3.8 and later also emits a SyntaxWarning: 'int' object is not callable; perhaps you missed a comma? for literals. Write 2 * (3 + 4).

Cause 3: a parameter or attribute with the same name as a function

A function parameter called max or len hides the built-in inside that function. A class that stores self.count = 0 and also defines a method count makes self.count() fail, because the instance attribute wins over the method. Give the data and the method different names.

Fix it

1. Read the line in the traceback and find the name followed by (.
2. Search upward for an assignment to that name.
3. Rename the assigned variable. If the name was assigned in an interactive session, run del name to expose the built-in again.
4. Run the code again to confirm that the call now reaches the function.

python3 - <<'PY'
sum = 10
del sum
print(sum([1, 2, 3]))
PY

6

Prevent it

Avoid names from dir(builtins) for your own variables, and use descriptive names such as total, largest or item_count. Linters (ruff rule A001 and flake8-builtins) flag assignments that shadow built-ins before the code runs.

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