TheAlgorithms/Python · error · ValueError

Empty string was passed to the function

Error message

Empty string was passed to the function

What it means

Raised by hex_to_decimal(hex_string) in conversions/hexadecimal_to_decimal.py:34 when the input strips to an empty string. The parser needs at least one hex digit; empty/whitespace-only input has nothing to evaluate, so it raises ValueError('Empty string was passed to the function') before the digit loop.

Source

Thrown at conversions/hexadecimal_to_decimal.py:34

    65535
    >>> hex_to_decimal("-Ff")
    -255
    >>> hex_to_decimal("F-f")
    Traceback (most recent call last):
        ...
    ValueError: Non-hexadecimal value was passed to the function
    >>> hex_to_decimal("")
    Traceback (most recent call last):
        ...
    ValueError: Empty string was passed to the function
    >>> hex_to_decimal("12m")
    Traceback (most recent call last):
        ...
    ValueError: Non-hexadecimal value was passed to the function
    """
    hex_string = hex_string.strip().lower()
    if not hex_string:
        raise ValueError("Empty string was passed to the function")
    is_negative = hex_string[0] == "-"
    if is_negative:
        hex_string = hex_string[1:]
    if not all(char in hex_table for char in hex_string):
        raise ValueError("Non-hexadecimal value was passed to the function")
    decimal_number = 0
    for char in hex_string:
        decimal_number = 16 * decimal_number + hex_table[char]
    return -decimal_number if is_negative else decimal_number


if __name__ == "__main__":
    from doctest import testmod

    testmod()

View on GitHub (pinned to f5988cc097)

Solutions

1. Filter or reject blank tokens upstream: if not hex_string.strip(): continue / raise
2. Treat empty as zero explicitly if that is your domain's semantics: hex_to_decimal(s or '0')
3. Add presence checks when parsing files so empty columns never propagate

Example fix

# before
for cell in row:
    out.append(hex_to_decimal(cell))  # empty cell -> ValueError

# after
for cell in row:
    if cell.strip():
        out.append(hex_to_decimal(cell))

if not isinstance(hex_string, str) or not hex_string.strip():
    raise ValueError('hex string is required')

def is_nonempty_hex_input(v: object) -> TypeGuard[str]:
    return isinstance(v, str) and bool(v.strip())

When it happens

Trigger: hex_to_decimal(''), hex_to_decimal('\t\n'), or an empty field from a form/parser flowing into the function.

Common situations: CSV rows with missing columns; JSON payloads where a hex field is present but empty; test harnesses iterating over possibly-empty tokens.

Related errors

• No value was passed to the function
• Non-hexadecimal value was passed to the function
• Empty string was passed to the function
• No input value was provided
• Invalid value was passed to the function

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/5646fc16ba79f196. Report an issue: GitHub.