TheAlgorithms/Python · error · ValueError

Missing an input

Error message

Missing an input

What it means

Raised by _validate_point() in maths/manhattan_distance.py when the point is falsy — None, an empty list [], or an empty container. The `if point:` guard treats any empty input as a missing value and raises ValueError('Missing an input') before any dimension checks run.

Source

Thrown at maths/manhattan_distance.py:78

    >>> _validate_point("not_a_list")
    Traceback (most recent call last):
         ...
    TypeError: Expected a list of numbers as input, found str
    """
    if point:
        if isinstance(point, list):
            for item in point:
                if not isinstance(item, (int, float)):
                    msg = (
                        "Expected a list of numbers as input, found "
                        f"{type(item).__name__}"
                    )
                    raise TypeError(msg)
        else:
            msg = f"Expected a list of numbers as input, found {type(point).__name__}"
            raise TypeError(msg)
    else:
        raise ValueError("Missing an input")


def manhattan_distance_one_liner(point_a: list, point_b: list) -> float:
    """
    Version with one liner

    >>> manhattan_distance_one_liner([1,1], [2,2])
    2.0
    >>> manhattan_distance_one_liner([1.5,1.5], [2,2])
    1.0
    >>> manhattan_distance_one_liner([1.5,1.5], [2.5,2])
    1.5
    >>> manhattan_distance_one_liner([-3, -3, -3], [0, 0, 0])
    9.0
    >>> manhattan_distance_one_liner([1,1], None)
    Traceback (most recent call last):
         ...
    ValueError: Missing an input

View on GitHub (pinned to f5988cc097)

Solutions

1. Ensure both points contain data before calling; skip or impute empty records upstream.
2. Default to a zero vector of the right dimension if an 'empty' point is semantically valid in your domain.
3. Check `if not point_a or not point_b: ...` in your own code to handle the case explicitly.

Example fix

# before
manhattan_distance([], [1, 2])

# after
if point_a and point_b:
    d = manhattan_distance(point_a, point_b)
else:
    d = 0.0  # or skip the record

if not point_a or not point_b:
    raise ValueError('both points are required')  # or skip/impute the record

def is_non_empty_list(p) -> bool:
    return isinstance(p, list) and len(p) > 0

When it happens

Trigger: manhattan_distance([], [1,2]), manhattan_distance(None, [1,2]), or a point loaded from a row that was never populated (defaults to []).

Common situations: Empty vectors from filtered-out data, default-argument accumulation bugs where a list stays empty, or None leaking through optional fields.

Related errors

• The list is empty. Provide a non-empty list.
• Both points must be in the same n-dimensional space
• The order must be greater than or equal to 1.
• Both points must have the same dimension.
• surface_area_cube() only accepts non-negative values

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/7210dcc91bf33f67. Report an issue: GitHub.