binary search in python3

Algorithms/Search/binary_search.py

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+"""
+Binary Search Implementation using recursion
+"""
+
+def binary_search(arr, x, y, z):
+    if y >= x:
+        mid = 1 + (y-1)//2
+
+        if arr[mid] == z:
+            return mid
+        elif arr[mid] > z:
+            return binary_search(arr, x, mid-1, z)
+        else:
+            return binary_search(arr, mid+1, y, z)
+
+    else:
+        return -1
+
+
+# tests
+
+arr = [10, 20, 30, 100, 40, 200]
+z = 100
+
+ret = binary_search(arr, 0, len(arr)-1, z)
+print(ret)
+