TheAlgorithms/Python · error · ValueError

parameter must be positive int

Error message

parameter must be positive int

What it means

decimal_to_any raises ValueError('parameter must be positive int') when num < 0. The repeated-division algorithm (divmod until the quotient reaches 1) assumes a positive dividend; negatives would loop incorrectly. Note the message says 'positive' but 0 is accepted, and the float TypeError check runs before this, so only negative ints land here.

Source

Thrown at conversions/decimal_to_any.py:63

    >>> decimal_to_any(10, '16') # doctest: +ELLIPSIS
    Traceback (most recent call last):
        ...
    TypeError: 'str' object cannot be interpreted as an integer
    >>> # a base less than 2 will error
    >>> decimal_to_any(7, 0) # doctest: +ELLIPSIS
    Traceback (most recent call last):
        ...
    ValueError: base must be >= 2
    >>> # a base greater than 36 will error
    >>> decimal_to_any(34, 37) # doctest: +ELLIPSIS
    Traceback (most recent call last):
        ...
    ValueError: base must be <= 36
    """
    if isinstance(num, float):
        raise TypeError("int() can't convert non-string with explicit base")
    if num < 0:
        raise ValueError("parameter must be positive int")
    if isinstance(base, str):
        raise TypeError("'str' object cannot be interpreted as an integer")
    if isinstance(base, float):
        raise TypeError("'float' object cannot be interpreted as an integer")
    if base in (0, 1):
        raise ValueError("base must be >= 2")
    if base > 36:
        raise ValueError("base must be <= 36")
    new_value = ""
    mod = 0
    div = 0
    while div != 1:
        div, mod = divmod(num, base)
        if base >= 11 and 9 < mod < 36:
            actual_value = ALPHABET_VALUES[str(mod)]
        else:
            actual_value = str(mod)
        new_value += actual_value

View on GitHub (pinned to f5988cc097)

Solutions

1. Handle the sign yourself: convert abs(num) and prefix '-' (or two's-complement for fixed width)
2. Clamp at the source if negatives are invalid in your domain: max(0, num)
3. Catch this ValueError alongside the TypeError/ValueError base checks when user input flows through

Example fix

# before
decimal_to_any(-10, 2)
# ValueError: parameter must be positive int

# after
sign = '-' if n < 0 else ''
sign + decimal_to_any(abs(-10), 2)  # '-1010'

if num < 0:
    sign, num = '-', -num
else:
    sign = ''
result = sign + decimal_to_any(num, base)

def is_non_negative_int(v) -> bool:
    return isinstance(v, int) and not isinstance(v, bool) and v >= 0

try:
    decimal_to_any(num, base)
except ValueError as e:
    if 'positive int' in str(e):
        return '-' + decimal_to_any(-num, base)
    raise

When it happens

Trigger: decimal_to_any(-7, 2), decimal_to_any(-255, 16); computing deltas/offsets that can go negative and passing them unclamped.

Common situations: Temperature/difference conversions; arithmetic on unsigned-vs-signed mixes; tests that sweep negative values through every conversion helper.

Related errors

• Invalid 'from_type' value: {from_type!r}.\nConversion abbrev
• Invalid 'to_type' value: {to_type!r}.\nConversion abbreviati
• Empty string was passed to the function
• Non-binary value was passed to the function
• Non-binary value was passed to the function

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/ea970cd9bd702e8b. Report an issue: GitHub.