def _read_num(  # noqa: C901  # pylint: disable=too-many-statements
    ctx: ReaderContext
) -> MaybeNumber:
    """Return a numeric (complex, Decimal, float, int, Fraction) from the input stream."""
    chars: List[str] = []
    reader = ctx.reader

    is_complex = False
    is_decimal = False
    is_float = False
    is_integer = False
    is_ratio = False
    while True:
        token = reader.peek()
        if token == "-":
            following_token = reader.next_token()
            if not begin_num_chars.match(following_token):
                reader.pushback()
                try:
                    for _ in chars:
                        reader.pushback()
                except IndexError:
                    raise SyntaxError(
                        "Requested to pushback too many characters onto StreamReader"
                    )
                return _read_sym(ctx)
            chars.append(token)
            continue
        elif token == ".":
            if is_float:
                raise SyntaxError("Found extra '.' in float; expected decimal portion")
            is_float = True
        elif token == "J":
            if is_complex:
                raise SyntaxError("Found extra 'J' suffix in complex literal")
            is_complex = True
        elif token == "M":
            if is_decimal:
                raise SyntaxError("Found extra 'M' suffix in decimal literal")
            is_decimal = True
        elif token == "N":
            if is_integer:
                raise SyntaxError("Found extra 'N' suffix in integer literal")
            is_integer = True
        elif token == "/":
            if is_ratio:
                raise SyntaxError("Found extra '/' in ratio literal")
            is_ratio = True
        elif not num_chars.match(token):
            break
        reader.next_token()
        chars.append(token)

    assert len(chars) > 0, "Must have at least one digit in integer or float"

    s = "".join(chars)
    if (
        sum(
            [
                is_complex and is_decimal,
                is_complex and is_integer,
                is_complex and is_ratio,
                is_decimal or is_float,
                is_integer,
                is_ratio,
            ]
        )
        > 1
    ):
        raise SyntaxError(f"Invalid number format: {s}")

    if is_complex:
        imaginary = float(s[:-1]) if is_float else int(s[:-1])
        return complex(0, imaginary)
    elif is_decimal:
        try:
            return decimal.Decimal(s[:-1])
        except decimal.InvalidOperation:
            raise SyntaxError(f"Invalid number format: {s}") from None
    elif is_float:
        return float(s)
    elif is_ratio:
        assert "/" in s, "Ratio must contain one '/' character"
        num, denominator = s.split("/")
        return Fraction(numerator=int(num), denominator=int(denominator))
    elif is_integer:
        return int(s[:-1])
    return int(s)
Return a numeric (complex, Decimal, float, int, Fraction) from the input stream.