TheAlgorithms/Python · error · TypeError

Unsupported type given for another ({type(another)})

Error message

Unsupported type given for another ({type(another)})

What it means

Raised by the local Matrix class's multiplication method in sherman_morrison when the right operand is neither a number nor a Matrix instance. This standalone Matrix class (used for the Sherman-Morrison inverse-update algorithm) only supports scalar multiplication and matrix multiplication; anything else — strings, nested lists, numpy arrays — is rejected with a TypeError naming the offending type.

Source

Thrown at matrix/sherman_morrison.py:178

        """

        if isinstance(another, (int, float)):  # Scalar multiplication
            result = Matrix(self.row, self.column)
            for r in range(self.row):
                for c in range(self.column):
                    result[r, c] = self[r, c] * another
            return result
        elif isinstance(another, Matrix):  # Matrix multiplication
            assert self.column == another.row
            result = Matrix(self.row, another.column)
            for r in range(self.row):
                for c in range(another.column):
                    for i in range(self.column):
                        result[r, c] += self[r, i] * another[i, c]
            return result
        else:
            msg = f"Unsupported type given for another ({type(another)})"
            raise TypeError(msg)

    def transpose(self) -> Matrix:
        """
        <method Matrix.transpose>
        Return self^T.
        Example:
        >>> a = Matrix(2, 3)
        >>> for r in range(2):
        ...     for c in range(3):
        ...             a[r,c] = r*c
        ...
        >>> a.transpose()
        Matrix consist of 3 rows and 2 columns
        [0, 0]
        [0, 1]
        [0, 2]
        """

View on GitHub (pinned to f5988cc097)

Solutions

1. Read the type in the error message to identify the culprit operand.
2. Wrap nested lists in this module's Matrix class before multiplying.
3. Convert NumPy arrays to plain numbers or to this Matrix type; or move the whole computation into NumPy.
4. Check for None operands (failed initialization/lookup) before the multiply.

Example fix

# before
result = a * [[1, 0], [0, 1]]  # TypeError: got <class 'list'>

# after
result = a * Matrix(2, 2, [[1, 0], [0, 1]])  # or however the class constructor takes data

def as_sherman_matrix(x, MatrixCls):
    """Wrap nested lists in this module's Matrix; pass numbers and Matrix through."""
    if isinstance(x, (int, float)) or isinstance(x, MatrixCls):
        return x
    if isinstance(x, (list, tuple)):
        return MatrixCls(len(x), len(x[0]), x)
    raise TypeError(f"unsupported operand {type(x).__name__}")

result = a * as_sherman_matrix(other, Matrix)

def is_mul_operand(x, MatrixCls) -> bool:
    """Guard: number or this module's Matrix instance."""
    return isinstance(x, (int, float)) or isinstance(x, MatrixCls)

try:
    result = a * operand
except TypeError as e:
    if "Unsupported type given for another" in str(e):
        # message names the actual type; fix the operand at its source
        raise TypeError(f"bad operand came from upstream: {operand!r}") from e
    raise

When it happens

Trigger: sherman_morrison_matrix * [[1, 0], [0, 1]] (raw list), matrix * np.array(...), or matrix * None (a variable that failed to initialize). The f-string in the message tells you exactly which type arrived, e.g. 'Unsupported type given for another (<class \"list\">)'.

Common situations: Interoperating with NumPy arrays; passing unwrapped nested-list test fixtures; None leaking in from a failed lookup of a second matrix; feeding data straight from JSON.

Related errors

• A Matrix can only be multiplied by an int, float, or another
• A Matrix can only be raised to the power of an int
• Step size must be an integer.
• Expected a matrix, got int/list instead
• The input value of 'num_rows' should be 'int'

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/eb20a23917a43563. Report an issue: GitHub.