#Binary Search in python3

#Define an array with elements

array = [2,3,5,7,11,13,17,19,23,27,29]

startingIndex = 0

lastIndex = len(array) - 1

middleIndex = (startingIndex + lastIndex) // 2

print ("Defined array's elements are - " +str(array))

target = int(input("Enter a value of a element in defined array :"))

flag = 0

while flag == 0:

if lastIndex > startingIndex:

middleIndex = (startingIndex + lastIndex)//2

if array[middleIndex] == target :

print ("The index of the element " + str(target) + " is " + str(middleIndex))

flag=1

elif array[middleIndex + 1] == target :

print ("The index of the element " + str(target) + " is " + str(middleIndex+1))

flag = 1

elif array[middleIndex] < target:

startingIndex = middleIndex + 1

elif array[middleIndex] > target:

lastIndex = middleIndex - 1

else:

print ("This value is not in the array as a element")

flag = 1