为什么我在 Python 中有快速排序的最大递归深度？

Question

I am trying to implement the quick sort based on a pseudocode I was given, and I understand how the algorithm works.
When I run a test on the function and the input list is randomized, it runs perfectly fine.
Yet, when I run a descending or ascending sorted list through the function I get the error of maximum recursion depth. To my understanding, it is because the pivot I chose was not randomized, as in inputs of elements 900 and under, the code works fine, but once I put 1000 elements for a list that is not randomized I receive that error. I am unsure how to go about randomizing it without using the rand function.
I also tried using the mid point, but my output is incorrect and I cannot figure out why.
Any help and explanation would be appreciated.

    def quicksort(self, query_list, left, right):
        if left < right:
            mid = self.partition(query_list, left, right)
            self.quicksort(query_list, left, mid - 1)
            self.quicksort(query_list, mid + 1, right)

    def partition(self, query_list, beg, end):
        pivot = query_list[end]
        i = beg - 1
        for j in range(beg, end):
            if query_list[j] >= pivot:
                i = i + 1
                (query_list[i], query_list[j]) = (query_list[j], query_list[i])
        (query_list[i + 1], query_list[end]) = (query_list[end], query_list[i + 1])
        return i + 1

Input a list rand: [3, 4, 8, 2, 0, 1]
Output: [8, 4, 3, 2, 1, 0]

I tried:

mid = (beg + end) // 2
pivot = query_list[mid]

My results:
Input list at random: [8, 2, 4, 1, 9, 3, 7, 10, 6, 5]
Output: [10, 9, 8, 6, 7, 1, 4, 3, 5, 2]

Answer 1

To use middle element as pivot with the Lomuto partition scheme used in the question, swap middle element with last element:

    def partition(self, query_list, beg, end):
        mid = (beg+end)/2
        query_list[mid],query_list[end] = query_list[end],query_list[mid]
        pivot = query_list[end]