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BinarySearch.py

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+""" 
+----------------------------------------
+Binary Search Algorithm 
+----------------------------------------
+The name is evident enough to give an overview of the project. 
+The program requires you to create a list of numbers between 0 
+to whatever range you prefer, with every succeeding number having 
+a difference of 2 between them. 
+
+When the user inputs a random number to be searched the program b
+egins its search by dividing the list into two halves. The first 
+half is searched for the required number and if found, the other half 
+is rejected and vice versa. The search continues until the number is 
+found or the subarray size becomes zero. This Python project idea could 
+also help you write a program to search an element in the list. 
+----------------------------------------
+"""
+
+# iterative implementation of binary search in Python
+def binary_search(a_list, item):
+    a_list = 'path/to/file/or/array'
+    """
+    Performs iterative binary search to find the position of an integer in a given, sorted, list.
+    a_list -- sorted list of integers
+    item -- integer you are searching for the position of
+    """
+    first = 0
+    last = len(a_list) - 1
+    while first <= last:
+        i = (first + last) / 2
+        if a_list[i] == item:
+            return ' found at position '.format(item=item, i=i)
+        elif a_list[i] > item:
+            last = i - 1
+        elif a_list[i] < item:
+            first = i + 1
+        else:
+            return ' not found in the list'.format(item=item)
+
+# recursive implementation of binary search in Python
+def binary_search_recursive(a_list, item):
+    """
+    Performs recursive binary search of an integer in a given, sorted, list.
+    a_list -- sorted list of integers
+    item -- integer you are searching for the position of
+    """
+    first = 0
+    last = len(a_list) - 1
+    if len(a_list) == 0:
+        return ' was not found in the list'.format(item=item)
+    else:
+        i = (first + last) // 2
+        if item == a_list[i]:
+            return ' found'.format(item=item)
+        else:
+            if a_list[i] < item:
+                return binary_search_recursive(a_list[i+1:], item)
+            else:
+                return binary_search_recursive(a_list[:i], item)