TheAlgorithms/Python · error · TypeError

k must be an integer.

Error message

k must be an integer.

What it means

Raised by the recursive fibonacci helper in searches/fibonacci_search.py when k is not an int. fibonacci_search uses Fibonacci numbers to pick probe offsets, and list indexing with a non-integer offset would be meaningless, so the helper hard-rejects non-int inputs with TypeError. Because isinstance(k, int) is the test, floats like 5.0 are rejected even though they are integer-valued, and bool passes (True/False are int subclasses).

Source

Thrown at searches/fibonacci_search.py:47

        Fibonacci number in position k.

    >>> fibonacci(0)
    0
    >>> fibonacci(2)
    1
    >>> fibonacci(5)
    5
    >>> fibonacci(15)
    610
    >>> fibonacci('a')
    Traceback (most recent call last):
    TypeError: k must be an integer.
    >>> fibonacci(-5)
    Traceback (most recent call last):
    ValueError: k integer must be greater or equal to zero.
    """
    if not isinstance(k, int):
        raise TypeError("k must be an integer.")
    if k < 0:
        raise ValueError("k integer must be greater or equal to zero.")
    if k == 0:
        return 0
    elif k == 1:
        return 1
    else:
        return fibonacci(k - 1) + fibonacci(k - 2)


def fibonacci_search(arr: list, val: int) -> int:
    """A pure Python implementation of a fibonacci search algorithm.

    Parameters
    ----------
    arr
        List of sorted elements.
    val

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass a plain Python int: fibonacci(10).
2. Coerce at the boundary: fibonacci(int(k)) after confirming no data loss (e.g. k == int(k)).
3. For values loaded from JSON, convert with int() before calling the helper.

Example fix

# before
fibonacci(float(user_input))  # e.g. 15.0 -> TypeError

# after
fibonacci(int(float(user_input)))  # or int(user_input) for plain digit strings

if not isinstance(k, int) or isinstance(k, bool):
    k = int(k)  # or raise TypeError
fibonacci(k)

def is_int_index(k) -> bool:
    return isinstance(k, int) and not isinstance(k, bool)

try:
    fib_k = fibonacci(k)
except TypeError:
    fib_k = fibonacci(int(k))

When it happens

Trigger: fibonacci('a'); fibonacci(10.0); fibonacci_search internals are safe because they only pass ints, so this error almost always comes from calling the helper directly with a value parsed from JSON/config (where numbers arrive as float or string).

Common situations: json.load produces floats for values like 10.0; CLI args passed as strings; numpy scalar types (np.int64 is fine on most builds but np.float64 is not an int).

Related errors

• k integer must be greater or equal to zero.
• 'float' object cannot be interpreted as an integer
• 'float' object cannot be interpreted as an integer
• iterations must be defined as integers
• All weights must be integers but got weight of type {type(wt

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/724cef7a2e89d6fa. Report an issue: GitHub.