TheAlgorithms/Python · error · ValueError

Barcode '{barcode}' has alphabetic characters.

Error message

Barcode '{barcode}' has alphabetic characters.

What it means

Raised by get_barcode in strings/barcode_validator.py when the barcode argument consists entirely of alphabetic characters (str(barcode).isalpha() is True). The helper converts the barcode to an int for checksum validation, and pure-letter input cannot be a barcode, so it is rejected with ValueError. Caveat: the isalpha() guard is narrow — mixed alphanumeric input like 'ab12' or '12ab' passes it and then crashes at int(barcode) with a different, uncaught ValueError from Python itself.

Source

Thrown at strings/barcode_validator.py:69

    NameError: name 'dwefgiweuf' is not defined
    """
    return len(str(barcode)) == 13 and get_check_digit(barcode) == barcode % 10


def get_barcode(barcode: str) -> int:
    """
    Returns the barcode as an integer

    >>> get_barcode("8718452538119")
    8718452538119
    >>> get_barcode("dwefgiweuf")
    Traceback (most recent call last):
        ...
    ValueError: Barcode 'dwefgiweuf' has alphabetic characters.
    """
    if str(barcode).isalpha():
        msg = f"Barcode '{barcode}' has alphabetic characters."
        raise ValueError(msg)
    elif int(barcode) < 0:
        raise ValueError("The entered barcode has a negative value. Try again.")
    else:
        return int(barcode)


if __name__ == "__main__":
    import doctest

    doctest.testmod()
    """
    Enter a barcode.

    """
    barcode = get_barcode(input("Barcode: ").strip())

    if is_valid(barcode):
        print(f"'{barcode}' is a valid barcode.")

View on GitHub (pinned to f5988cc097)

Solutions

1. Validate with str.isdigit() before calling: if not barcode.isdigit(): reject. This also covers the mixed-alphanumeric gap.
2. Normalize input: strip whitespace and reject non-digit characters at the boundary of your application.
3. If you hit this from user input, prompt again instead of catching and continuing with a bad value.

Example fix

# before
get_barcode(user_input)  # user typed 'dwefgiweuf'

# after
if not user_input.strip().isdigit():
    raise ValueError('Barcode must contain digits only')
get_barcode(user_input.strip())

code = str(barcode).strip()
if not code.isdigit():
    raise ValueError('Barcode must contain digits only')
value = get_barcode(code)

def is_digit_string(s: str) -> bool:
    return isinstance(s, str) and s.isdigit()

try:
    value = get_barcode(user_input.strip())
except ValueError as e:
    # covers alphabetic, negative, and int() parse failures
    show_error_to_user(str(e))
    value = ask_for_barcode_again()

When it happens

Trigger: get_barcode('dwefgiweuf'); get_barcode('abc'). Passing 'ab123' does NOT hit this error — it fails later at int('ab123') with ValueError: invalid literal for int().

Common situations: Form fields where users type a product name into the barcode box; OCR output that read letters; test fixtures with placeholder strings.

Related errors

• The entered barcode has a negative value. Try again.
• invalid input option
• Invalid Strand
• String lengths must match!
• Input value must be a positive integer

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/eae0329f674546f9. Report an issue: GitHub.