下面代码是寻找水仙花数的程序，横线处应该填写的代码是（ ）。
【是指一个n位数（n≥3），其每位数字的n次幂之和等于它本身】
def is_narcissistic_num(num):
str_num = str(num)
num_digits = len(str_num)
———————————
return num == sum_of_powers
for i in range(100, 10000):
if is_narcissistic_num(i):
print(i, "是水仙花数")
```Python
sum_of_powers = sum(int(digit) ** num_digits for digit in num)
```Python
sum_of_powers = sum(int(digit) ** num for digit in str_num)
```Python
sum_of_powers = sum(int(num) ** num_digits for digit in str_num)
```Python
sum_of_powers = sum(int(digit) ** num_digits for digit in str_num)