TheAlgorithms/Python · error · ValueError

Expected b_coeffs to have {self.order + 1} elements for {sel

Error message

Expected b_coeffs to have {self.order + 1} elements for {self.order}-order filter, got {len(a_coeffs)}

What it means

Raised by capture_radii() in physics/basic_orbital_capture.py when the target body's radius is negative. The radius is used both as a divisor in the escape-velocity-squared term and as a multiplier of the capture radius, so a negative value produces a nonsensical (and negative under the sqrt argument) result. The guard fires immediately after the mass check, before the velocity check.

Source

Thrown at audio_filters/iir_filter.py:70

        >>> filt = IIRFilter(2)
        >>> filt.set_coefficients(a_coeffs, b_coeffs)
        """
        if len(a_coeffs) < self.order:
            a_coeffs = [1.0, *a_coeffs]

        if len(a_coeffs) != self.order + 1:
            msg = (
                f"Expected a_coeffs to have {self.order + 1} elements "
                f"for {self.order}-order filter, got {len(a_coeffs)}"
            )
            raise ValueError(msg)

        if len(b_coeffs) != self.order + 1:
            msg = (
                f"Expected b_coeffs to have {self.order + 1} elements "
                f"for {self.order}-order filter, got {len(a_coeffs)}"
            )
            raise ValueError(msg)

        self.a_coeffs = a_coeffs
        self.b_coeffs = b_coeffs

    def process(self, sample: float) -> float:
        """
        Calculate :math:`y[n]`

        >>> filt = IIRFilter(2)
        >>> filt.process(0)
        0.0
        """
        result = 0.0

        # Start at index 1 and do index 0 at the end.
        for i in range(1, self.order + 1):
            result += (
                self.b_coeffs[i] * self.input_history[i - 1]

View on GitHub (pinned to f5988cc097)

Solutions

Verify target_body_radius is positive before calling; fix the source data.
Confirm the argument order: capture_radii(radius, mass, velocity) — radius is the first positional parameter.
If -1 is used as an 'unknown' sentinel, replace it with explicit None handling before the call.

Example fix

# before
capture_radii(radius_km * -1, mass, vel)  # sign slip

# after
capture_radii(abs(radius_km) * 1000, mass, vel)  # km -> m, positive

Defensive patterns

Strategy: validation

Validate before calling

if target_body_radius < 0:
    raise ValueError(f"target_body_radius must be >= 0, got {target_body_radius}")
radius = capture_radii(mass, target_body_radius, velocity)

Type guard

def is_valid_radius(r: object) -> bool:
    return isinstance(r, (int, float)) and not isinstance(r, bool) and r >= 0

Try / catch

try:
    r = capture_radii(m, R, v)
except ValueError as e:
    if "Radius" in str(e):
        R = abs(R)  # only if sign is a known artifact
    else:
        raise

Prevention

Use keyword arguments to avoid swapping mass and radius.
Keep units consistent (SI meters) across the pipeline.
Reject negative radii at parse time from external data.

When it happens

Trigger: Calling capture_radii(1.99e30, -6.957e8, 30000); passing a radius in the wrong unit scale or a radius derived as (diameter/2) with a sign typo; passing -1 as a sentinel 'unknown' value.

Common situations: Parsing radius data where a leading minus sign was accidental, mixing up argument order (radius passed where mass belongs), or using negative sentinel values (-1) for 'not configured' inputs.

Related errors

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/f2c1fd004e03742e. Report an issue: GitHub.