Sorting algorithm my implementation

Today I tried to implement sort in Python and faced a few problems and overcame them

The first problem was in the code below

inputlist = [54, 26, 93, 17, 17, 77, 31, 44, 55, 20]
def Sort(unsortedList):
    if len(unsortedList) > 1:
        left = [] # for smaller numbers (not deatl woth duplicat elements yet)
        right = [] # for bigger numbers
        pivot = len(unsortedList)//2 # write another using first element

        for i in unsortedList:
            if i < unsortedList[pivot]:
                left.append(i)
            elif i == unsortedList[pivot]:
                continue
            else:
                right.append(i)

        l = Sort(left)
        part = l.append(unsortedList[pivot]) # this line is responsible
        l.append(unsortedList[pivot])
        r = Sort(right)
        return part + r

    else:
        return unsortedList
print(Sort(inputlist))

When I ran this code, It showed an error as shown below

Traceback (most recent call last):
  File "_____.py", line 24, in <module>
    print(Sort(k))
          ^^^^^^^^^^^^
  File "_____.py", line 16, in Sort
    l = Sort(left)
        ^^^^^^^^^^^^^^^
  File "_____.py", line 16, in Sort
    l = Sort(left)
        ^^^^^^^^^^^^^^^
  File "_____.py", line 19, in Sort
    r = Sort(right)
        ^^^^^^^^^^^^^^^^
  File "_____.py", line 20, in Sort
    return part + r
           ~~~~~^~~
TypeError: unsupported operand type(s) for +: 'NoneType' and 'list'

By seeing this error I was sure that part or r one of those was not assigned properly, At first I thought r should be the one which is responsible for this error and on the line r = Sort(right) Sort(right) wasn't returning anything was my conclusion

Then I tried to print out things and found that part is the one responsible and the responsible line was part = l.append(unsortedList[pivot]) Because the append method is updating the list and won't return anything simply getting rid of the part variable was the solution and the corrected code is shown below

inputlist = [54, 26, 93, 17, 17, 77, 31, 44, 55, 20]
def Sort(unsortedList):
    if len(unsortedList) > 1:
        left = [] # for smaller numbers (not deatl woth duplicat elements yet)
        right = [] # for bigger numbers

        pivot = len(unsortedList)//2 # write another using first element
        for i in unsortedList:
            if i < unsortedList[pivot]:
                left.append(i)
            elif i == unsortedList[pivot]:
                continue
            else:
                right.append(i)

        l = Sort(left)
        l.append(unsortedList[pivot])
        r = Sort(right)
        return l + r
    else:
        return unsortedList
print(Sort(inputlist))

The story did not end here, As You can see in the first version of the code I simply neglected duplicate elements in the list. even if the list has duplicate elements they will be gone only one will remain in the output, so I re-write the code as below

# this version does deal with duplicate elements
k = [54, 26, 93, 17, 17, 77, 31, 44, 55, 20]
def Sort(unsortedList):
    if len(unsortedList) > 1:
        left = [] # smaller numbers than pivot 
        right = [] # bigger numbers than pivot
        equals = [] # equal numbers to pivot (to track how many duplicates are there)

        pivot = len(unsortedList)//2 
        for i in unsortedList:
            if i < unsortedList[pivot]:
                left.append(i)
            elif i == unsortedList[pivot]:
                equals.append(i)
            else:
                right.append(i)

        l = Sort(left)

        for equal in equals:
            l.append(equal)

        r = Sort(right)
        return l + r
    else:
        return unsortedList  
print(Sort(k))

Still story is not finished yet, you can see the pivot element is near to middle (not exactly in the middle), but I can change it to the first, second or last element by changing the line below as follows

pivot = len(unsortedList)//2 to pivot = 0 , pivot = 1 or pivot = -1