TheAlgorithms/Python · error · ValueError

solve_simultaneous() requires lists of integers

Error message

solve_simultaneous() requires lists of integers

What it means

Raised by solve_simultaneous() when any element of any equation row is not an int or float — e.g. a string like 'a', None, or a Decimal. Despite the message saying 'lists of integers', floats are accepted; only non-numeric types are rejected. This guard runs after the shape check, so a shape error masks it for malformed rows.

Source

Thrown at maths/simultaneous_linear_equation_solver.py:87

        ...
    IndexError: solve_simultaneous() requires n lists of length n+1
    >>> solve_simultaneous([[1, 2, 3],["a", 7, 8]])
    Traceback (most recent call last):
        ...
    ValueError: solve_simultaneous() requires lists of integers
    >>> solve_simultaneous([[0, 2, 3],[4, 0, 6]])
    Traceback (most recent call last):
        ...
    ValueError: solve_simultaneous() requires at least 1 full equation
    """
    if len(equations) == 0:
        raise IndexError("solve_simultaneous() requires n lists of length n+1")
    _length = len(equations) + 1
    if any(len(item) != _length for item in equations):
        raise IndexError("solve_simultaneous() requires n lists of length n+1")
    for row in equations:
        if any(not isinstance(column, (int, float)) for column in row):
            raise ValueError("solve_simultaneous() requires lists of integers")
    if len(equations) == 1:
        return [equations[0][-1] / equations[0][0]]
    data_set = equations.copy()
    if any(0 in row for row in data_set):
        temp_data = data_set.copy()
        full_row = []
        for row_index, row in enumerate(temp_data):
            if 0 not in row:
                full_row = data_set.pop(row_index)
                break
        if not full_row:
            raise ValueError("solve_simultaneous() requires at least 1 full equation")
        data_set.insert(0, full_row)
    useable_form = data_set.copy()
    simplified = simplify(useable_form)
    simplified = simplified[::-1]
    solutions: list = []
    for row in simplified:

View on GitHub (pinned to f5988cc097)

Solutions

1. Convert every element: [[float(x) for x in row] for row in equations]
2. Convert Decimal/Fraction values to float before calling
3. Validate numerics at parse time, not at solve time

Example fix

# before
rows = [line.split(',') for line in text.splitlines()]
solve_simultaneous(rows)  # strings -> ValueError

# after
rows = [[float(x) for x in line.split(',')] for line in text.splitlines()]
solve_simultaneous(rows)

equations = [[float(x) for x in row] for row in equations]
solve_simultaneous(equations)

def is_numeric_system(eq: list) -> bool:
    return all(
        isinstance(x, (int, float)) and not isinstance(x, bool)
        for row in eq for x in row
    )

try:
    solve_simultaneous(equations)
except ValueError as e:
    if 'lists of integers' in str(e):
        equations = [[float(x) for x in row] for row in equations]

When it happens

Trigger: Calling solve_simultaneous([[1, 2, 3], ['a', 7, 8]]). Very common when rows come from str.split() without int()/float() conversion — split yields strings even for '1'.

Common situations: Parsing equations from text files or stdin; rows coming from JSON with stringified numbers ('2' instead of 2); None placeholders for missing coefficients; mixing numpy scalars is fine (they subclass float/int) but Decimal and Fraction are NOT accepted and will raise.

Related errors

• Input series is not valid, valid series - [1, 2/3, 2]
• Input series is not valid, valid series - [2, 4, 6]
• solve_simultaneous() requires at least 1 full equation
• area_reg_polygon() only accepts integers greater than or equ
• Input list must be a non empty list

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/d30af46710e918ab. Report an issue: GitHub.