TheAlgorithms/Python · error · ValueError

Invalid source or destination coordinates

Error message

Invalid source or destination coordinates

What it means

Raised by center_of_mass() in physics/center_of_mass.py when any particle in the list has mass <= 0 (zero or negative). A zero-mass particle contributes nothing but still passes the emptiness check, and negative masses make the weighted average meaningless; total_mass could even become 0 and cause a ZeroDivisionError, so the library rejects them up front.

Source

Thrown at backtracking/rat_in_maze.py:127

    >>> solve_maze(maze,2,0,len(maze)-1,len(maze)-1)
    Traceback (most recent call last):
        ...
    ValueError: Invalid source or destination coordinates

    >>> maze = [[1, 0, 0],
    ...         [0, 1, 0],
    ...         [1, 0, 0]]
    >>> solve_maze(maze,0,1,len(maze),len(maze)-1)
    Traceback (most recent call last):
        ...
    ValueError: Invalid source or destination coordinates
    """
    size = len(maze)
    # Check if source and destination coordinates are Invalid.
    if not (0 <= source_row <= size - 1 and 0 <= source_column <= size - 1) or (
        not (0 <= destination_row <= size - 1 and 0 <= destination_column <= size - 1)
    ):
        raise ValueError("Invalid source or destination coordinates")
    # We need to create solution object to save path.
    solutions = [[1 for _ in range(size)] for _ in range(size)]
    solved = run_maze(
        maze, source_row, source_column, destination_row, destination_column, solutions
    )
    if solved:
        return solutions
    else:
        raise ValueError("No solution exists!")


def run_maze(
    maze: list[list[int]],
    i: int,
    j: int,
    destination_row: int,
    destination_column: int,
    solutions: list[list[int]],

View on GitHub (pinned to f5988cc097)

Solutions

1. Verify Particle field order is (x, y, z, mass) at every construction site.
2. Filter or repair particles before the call: [p for p in particles if p.mass > 0].
3. Treat mass<=0 rows in source data as corrupt and log/skip them.

Example fix

# before
com = center_of_mass(all_particles)  # some have mass 0

# after
valid = [p for p in all_particles if p.mass > 0]
com = center_of_mass(valid) if valid else None

valid = [p for p in particles if p.mass > 0]
if not valid:
    raise ValueError("no particles with positive mass")
com = center_of_mass(valid)

from collections import namedtuple
Particle = namedtuple('Particle', 'x y z mass')
def has_valid_masses(ps: list) -> bool:
    return all(p.mass > 0 for p in ps)

try:
    com = center_of_mass(particles)
except ValueError as e:
    if "Mass" in str(e):
        bad = [i for i, p in enumerate(particles) if p.mass <= 0]
        raise ValueError(f"non-positive mass at indices {bad}") from e
    raise

When it happens

Trigger: center_of_mass([Particle(0, 0, 0, 0)]); any list containing a Particle whose mass field is 0 or negative, e.g. Particle(9, 10, 11, 0) or Particle(1, 2, 3, -5).

Common situations: Field-order mistakes when constructing Particle(x, y, z, mass) — putting mass in the wrong slot; imported data with missing masses defaulted to 0; placeholder particles added with mass 0.

Related errors

• Expected a_coeffs to have {self.order + 1} elements for {sel
• Expected b_coeffs to have {self.order + 1} elements for {sel
• k must not be negative
• n must not be negative
• All elements in candidates must be non-negative

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/07275db2de396aaa. Report an issue: GitHub.