求助，刚学python，这个一直显示数组越界怎么解决IndexError: list index out of range

#随机选取一个真实用户
userIndex = random.randint(0,len(allUserLocation))
realUserLocation = allUserLocation[userIndex]
print(len(allUserLocation))
del allUserLocation[userIndex]
print(len(allUserLocation))

Traceback (most recent call last):
File "C:/Users/Zhang Liqiang/Desktop/lbs/lbs_algorithm/lbs_algorithm/test_algorithm/showAllUser_geohash.py", line 17, in
realUserLocation = allUserLocation[userIndex]
IndexError: list index out of range

改成

userIndex = random.randint(0,len(allUserLocation)-1)

比如你有4个user ， 下标范围为 0-3
random.randint(0,4) 有可能取到 4

而 4 下标是不存在的。

因为例如random.randint(0,3)生成的随机数为0,1,2,3，当len(allUserLocation)恰好被生成时，allUserLocation[userIndex]会越界，数组的下标是从0开始计数的