TheAlgorithms/Python · error · TypeError

Not a Number

Error message

Not a Number

What it means

Raised by compute_geometric_mean in maths/geometric_mean.py when any element of args is neither int nor float. The function multiplies all arguments together to compute the geometric mean via an n-th root, so non-numeric values would break the arithmetic; each element is checked with isinstance and TypeError('Not a Number') is raised on the first offender.

Source

Thrown at maths/geometric_mean.py:33

        ...
    TypeError: Not a Number
    >>> compute_geometric_mean(5, 125)
    25.0
    >>> compute_geometric_mean(1, 0)
    0.0
    >>> compute_geometric_mean(1, 5, 25, 5)
    5.0
    >>> compute_geometric_mean(2, -2)
    Traceback (most recent call last):
        ...
    ArithmeticError: Cannot Compute Geometric Mean for these numbers.
    >>> compute_geometric_mean(-5, 25, 1)
    -5.0
    """
    product = 1
    for number in args:
        if not isinstance(number, int) and not isinstance(number, float):
            raise TypeError("Not a Number")
        product *= number
    # Cannot calculate the even root for negative product.
    # Frequently they are restricted to being positive.
    if product < 0 and len(args) % 2 == 0:
        raise ArithmeticError("Cannot Compute Geometric Mean for these numbers.")
    mean = abs(product) ** (1 / len(args))
    # Since python calculates complex roots for negative products with odd roots.
    if product < 0:
        mean = -mean
    # Since it does floating point arithmetic, it gives 64**(1/3) as 3.99999996
    possible_mean = float(round(mean))
    # To check if the rounded number is actually the mean.
    if possible_mean ** len(args) == product:
        mean = possible_mean
    return mean


if __name__ == "__main__":

View on GitHub (pinned to f5988cc097)

Solutions

1. Spread collections: call compute_geometric_mean(*nums) not compute_geometric_mean(nums).
2. Coerce numeric strings and Decimals to float before calling.
3. Filter None/missing values out of the data before computing the mean.

Example fix

// before
mean = compute_geometric_mean(data)  # data is a list -> TypeError

// after
mean = compute_geometric_mean(*data)

clean = [float(x) for x in args if x is not None]
mean = compute_geometric_mean(*clean)

def all_numeric(seq) -> bool:
    return all(isinstance(x, (int, float)) for x in seq)

try:
    m = compute_geometric_mean(*nums)
except TypeError as e:
    if 'Not a Number' in str(e):
        nums = [float(x) for x in nums]
        m = compute_geometric_mean(*nums)

When it happens

Trigger: Calling compute_geometric_mean(2, '3'), compute_geometric_mean([1,2,3]) (passing a list as a single arg), or with None/Decimal/bool-adjacent objects. Note bool passes isinstance(x, int), and a nested list fails.

Common situations: Passing an unspread list instead of *args; mixed data from JSON where numbers arrive as strings; None values from sparse data not filtered out.

Related errors

• Cannot Compute Geometric Mean for these numbers.
• List is empty
• List is empty
• successes must be lower or equal to trials
• the function is defined for non-negative integers

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/c087847856e573b9. Report an issue: GitHub.