TheAlgorithms/Python · error · ValueError

Incorrect 'from_type' or 'to_type' value: {unit_from!r}, {un

Error message

Incorrect 'from_type' or 'to_type' value: {unit_from!r}, {unit_to!r}
Valid values are: {', '.join(speed_chart_inverse)}

What it means

Raised by convert_speed() in conversions/speed_conversions.py when unit_to is not a key of speed_chart or unit_from is not a key of speed_chart_inverse (same unit set). Valid units are km/h, mph, knot, m/s (exact strings). The ValueError message lists the valid values.

Source

Thrown at conversions/speed_conversions.py:64

    >>> convert_speed(100, "mph", "km/h")
    160.934
    >>> convert_speed(100, "mph", "m/s")
    44.704
    >>> convert_speed(100, "mph", "knot")
    86.898
    >>> convert_speed(100, "knot", "km/h")
    185.2
    >>> convert_speed(100, "knot", "m/s")
    51.444
    >>> convert_speed(100, "knot", "mph")
    115.078
    """
    if unit_to not in speed_chart or unit_from not in speed_chart_inverse:
        msg = (
            f"Incorrect 'from_type' or 'to_type' value: {unit_from!r}, {unit_to!r}\n"
            f"Valid values are: {', '.join(speed_chart_inverse)}"
        )
        raise ValueError(msg)
    return round(speed * speed_chart[unit_from] * speed_chart_inverse[unit_to], 3)


if __name__ == "__main__":
    import doctest

    doctest.testmod()

View on GitHub (pinned to f5988cc097)

Solutions

1. Use exactly one of: km/h, mph, knot, m/s.
2. Add an alias map at your boundary: {'kph': 'km/h', 'kmh': 'km/h', 'knots': 'knot', 'mps': 'm/s'}.
3. If you need ft/s or other units, convert yourself via m/s (1 ft/s = 0.3048 m/s) after calling with m/s.

Example fix

# before
convert_speed(100, 'kph', 'mph')  # ValueError: Incorrect 'from_type' or 'to_type' value

# after
ALIASES = {'kph': 'km/h', 'kmh': 'km/h', 'knots': 'knot', 'mph': 'mph'}
convert_speed(100, ALIASES['kph'], 'mph')  # 62.137

from conversions.speed_conversions import speed_chart_inverse

unit_from = ALIASES.get(unit_from.lower(), unit_from)
unit_to = ALIASES.get(unit_to.lower(), unit_to)
if unit_from not in speed_chart_inverse or unit_to not in speed_chart_inverse:
    raise ValueError(f'unsupported speed unit(s) {unit_from!r}, {unit_to!r}')
convert_speed(speed, unit_from, unit_to)

from conversions.speed_conversions import speed_chart_inverse

def is_speed_unit(u: object) -> bool:
    return isinstance(u, str) and u in speed_chart_inverse

try:
    convert_speed(v, f, t)
except ValueError as e:
    if 'Incorrect' in str(e):
        raise UserInputError(f'unsupported speed unit: {f!r} -> {t!r}') from e
    raise

When it happens

Trigger: Calling convert_speed(100, 'KM/H', 'mph') (case), convert_speed(100, 'kph', 'mph') (alias), or convert_speed(100, 'ft/s', 'm/s') (unsupported unit).

Common situations: UI dropdowns using display labels like 'Kilometers per hour' instead of the library's tokens; synonyms (kph, kmh, kmph) not matching 'km/h'; adding units like ft/s or mach that the chart does not contain.

Related errors

• Invalid 'from_type' value: {from_type!r} Supported values a
• Invalid 'to_type' value: {to_type!r}. Supported values are:
• 'time_value' must be a non-negative number.
• Invalid unit {invalid_unit} is not in {', '.join(time_chart)
• Invalid 'from_type' value: {from_type!r} Supported values a

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/4ddb305eb157b966. Report an issue: GitHub.