Add Python doctests to quicksort.py (#166)

* Add Python doctests to quicksort.py

* quicksort(list(reversed(ascii_letters)))

* Update quick-sort.py

sorting/python/quick-sort.py

@@ -1,12 +1,22 @@
-def quickSort(arr):
-    n = len(arr)
-    if n == 1 or n == 0:
+arr = [10, 1, 6, 256, 2, 53, 235, 53, 1, 7, 0, -23, 23]
+
+
+def quicksort(arr):
+    """
+    >>> quicksort(arr)
+    [-23, 0, 1, 1, 2, 6, 7, 10, 23, 53, 53, 235, 256]
+    >>> from string import ascii_letters
+    >>> quicksort(list(reversed(ascii_letters))) == sorted(ascii_letters)
+    True
+    """
+    length = len(arr)
+    if length in (0, 1):
         return arr
     pi = 0
-    left = [arr[i] for i in range(n) if arr[i] <= arr[pi] and i != pi]
-    right = [arr[i] for i in range(n) if arr[i] > arr[pi]]
-    return quickSort(left) + [arr[pi]] + quickSort(right)
+    left = [arr[i] for i in range(length) if arr[i] <= arr[pi] and i != pi]
+    right = [arr[i] for i in range(length) if arr[i] > arr[pi]]
+    return quicksort(left) + [arr[pi]] + quicksort(right)
 
 
-arr = [10, 1, 6, 256, 2, 53, 235, 53, 1, 7, 23]
-print("Sorted Array:", quickSort(arr))
+if __name__ == "__main__":
+    print("Sorted Array:", quicksort(arr))