[Python] Why can't my Python code properly sort a list of numbers using the quick sort...

I am using Python and trying to implement quick sort but it is not working as expected. I am providing my code below:

def quicksort(arr):
if len(arr) <= 1:
return arr
pivot = arr[0]
left = [x for x in arr[1:] if x < pivot]
right = [x for x in arr[1:] if x >= pivot]
return quicksort(left) + [pivot] + quicksort(right)

arr = [10, 2, 30, 5, 7]
print(quicksort(arr))


Problem: Instead of returning a sorted list, the code sometimes gives unexpected results. What I tried: I tried to change the division into left and right elements, but that didn't work. Expected result: I expect the list to be sorted in ascending order.

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