TheAlgorithms/Python · error · TypeError

'str' object cannot be interpreted as an integer

Error message

'str' object cannot be interpreted as an integer

What it means

Raised by decimal_to_binary_iterative(num) in conversions/decimal_to_binary.py:33 when `num` is a str. The function does no string parsing — not even numeric strings like '0xfffff' or '42' — because the shift/modulo loop requires an int. Callers must parse strings themselves before calling.

Source

Thrown at conversions/decimal_to_binary.py:33

    >>> # negatives work too
    >>> decimal_to_binary_iterative(-2)
    '-0b10'
    >>> # other floats will error
    >>> decimal_to_binary_iterative(16.16) # doctest: +ELLIPSIS
    Traceback (most recent call last):
        ...
    TypeError: 'float' object cannot be interpreted as an integer
    >>> # strings will error as well
    >>> decimal_to_binary_iterative('0xfffff') # doctest: +ELLIPSIS
    Traceback (most recent call last):
        ...
    TypeError: 'str' object cannot be interpreted as an integer
    """

    if isinstance(num, float):
        raise TypeError("'float' object cannot be interpreted as an integer")
    if isinstance(num, str):
        raise TypeError("'str' object cannot be interpreted as an integer")

    if num == 0:
        return "0b0"

    negative = False

    if num < 0:
        negative = True
        num = -num

    binary: list[int] = []
    while num > 0:
        binary.insert(0, num % 2)
        num >>= 1

    if negative:
        return "-0b" + "".join(str(e) for e in binary)

View on GitHub (pinned to f5988cc097)

Solutions

1. Parse the string yourself first: decimal_to_binary_iterative(int('42')) for decimal, int('0xfffff', 0) or int(s, 16) for hex
2. For raw user input, wrap parsing in try/except ValueError to surface a friendly message
3. Note decimal_to_binary_recursive (same module) does accept strings — switch to it if string input is the norm

Example fix

# before
decimal_to_binary_iterative('0xfffff')  # TypeError

# after
decimal_to_binary_iterative(int('0xfffff', 16))  # '0b11111111111111111111'

if isinstance(num, str):
    num = int(num)          # decimal strings
    # or int(num, 16) / int(num, 0) for prefixed strings

def is_int_not_str(v: object) -> TypeGuard[int]:
    return isinstance(v, int)

When it happens

Trigger: decimal_to_binary_iterative('0xfffff'), decimal_to_binary_iterative('42'), or forwarding raw stdin/argparse/UI input into the function.

Common situations: Feeding CLI arguments (always strings) or file/network payloads directly to the converter; assuming the function is lenient like int() itself.

Related errors

• 'float' object cannot be interpreted as an integer
• operation can not be conducted on an object of type {type(nu
• Input value must be an 'int' type
• plaintext must be a string
• key must be a string

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/f337d2632939304a. Report an issue: GitHub.