排序题

CodeWars上的排序题
Your task is to make a function that can take any non-negative integer as a argument and return it with its digits in descending order.
Essentially, rearrange the digits to create the highest possible number.
Examples:
Input: 21445 Output: 54421
Input: 145263 Output: 654321

Input: 1254859723 Output: 9875543221def descend_range(number):
num = []
if (number<0):
print("Please enter a non-negative number")
else:
for i in range(len(str(number))):
num.append(str(number)[i])
num = ''.join(sorted(num, reverse=True))
print(num)

num = 18754984586
descend_range(num)