Unsupported operand type(s) for -: 'int' and 'function'

Unsupported operand type(s) for -: 'int' and 'function' #

The Python "TypeError: unsupported operand type(s) for -: 'int' and 'function'" occurs when we try to use the subtraction - operator with an integer and a function. To solve the error, make sure to call the function, e.g. my_func().

Here is an example of how the error occurs.

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def get_num():
    return 25


# ⛔️ TypeError: unsupported operand type(s) for -: 'int' and 'function'
result = 50 - get_num

We forgot to invoke the get_num function so we ended up trying to subtract a function from an integer.

To solve the error, make sure to call the function.

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def get_num():
    return 25

# 👇️ use parenthesis to call function
result = 50 - get_num()

print(result)  # 👉️ 25

We used parenthesis to call the function, so we can get its return value.

You should be returning a number from the function as trying to subtract different types (e.g. a string and a number) would cause an error.

If you aren't sure what type a variable stores, use the built-in type() class.

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def get_num():
    return 25


print(type(get_num))  # 👉️ <class 'function'>
print(callable(get_num)) # 👉️ True

print(type(get_num()))  # 👉 <class 'int'>
print(isinstance(get_num(), int))  # 👉️ True

The type class returns the type of an object.

The isinstance function returns True if the passed in object is an instance or a subclass of the passed in class.

The callable function takes an object as an argument and returns True if the object appears callable, otherwise False is returned.

If the callable() function returns True, it is still possible that calling the object fails, however if it returns False, calling the object will never succeed.