TheAlgorithms/Python · error · ValueError

Empty string was passed to the function

Error message

Empty string was passed to the function

What it means

bin_to_decimal raises this ValueError when the input, after str() conversion and .strip(), is empty. The guard runs before any parsing, so an empty or all-whitespace string never reaches the digit loop. It exists to distinguish 'no input at all' from 'input that is not binary' (a separate error).

Source

Thrown at conversions/binary_to_decimal.py:28

    -29
    >>> bin_to_decimal("0")
    0
    >>> bin_to_decimal("a")
    Traceback (most recent call last):
        ...
    ValueError: Non-binary value was passed to the function
    >>> bin_to_decimal("")
    Traceback (most recent call last):
        ...
    ValueError: Empty string was passed to the function
    >>> bin_to_decimal("39")
    Traceback (most recent call last):
        ...
    ValueError: Non-binary value was passed to the function
    """
    bin_string = str(bin_string).strip()
    if not bin_string:
        raise ValueError("Empty string was passed to the function")
    is_negative = bin_string[0] == "-"
    if is_negative:
        bin_string = bin_string[1:]
    if not all(char in "01" for char in bin_string):
        raise ValueError("Non-binary value was passed to the function")
    decimal_number = 0
    for char in bin_string:
        decimal_number = 2 * decimal_number + int(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. Check the string is non-empty before calling: if not s.strip(): ...
2. Filter blank lines when processing files: (line for line in lines if line.strip())
3. Default missing input to '0' if an empty string should mean zero in your domain

Example fix

# before
bin_to_decimal(user_input)  # user pressed Enter
# ValueError: Empty string was passed to the function

# after
if not user_input.strip():
    raise ValueError('binary string required')
bin_to_decimal(user_input)

if not str(bin_string).strip():
    raise ValueError('binary string required')
bin_to_decimal(bin_string)

def is_nonempty_str(v) -> bool:
    return isinstance(v, str) and v.strip() != ''

try:
    bin_to_decimal(s)
except ValueError as e:
    if 'Empty string' in str(e):
        return 0  # or skip record
    raise

When it happens

Trigger: bin_to_decimal(''), bin_to_decimal(' '), bin_to_decimal(None) (str(None)='None' actually fails the binary check instead), bin_to_decimal(' \t ') — any input that is empty after trimming whitespace.

Common situations: Reading user input that was submitted blank; iterating over file lines where a trailing empty line is not filtered; variable initialized to '' and never set before the call.

Related errors

• Non-binary value was passed to the function
• Empty string was passed to the function
• Non-binary value was passed to the function
• Non-binary value was passed to the function
• Empty string was passed to the function

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/b63431987649216a. Report an issue: GitHub.