Python: Binary search

Last update on July 28 2025 12:57:18 (UTC/GMT +8 hours)

1. Binary Search

Write a Python program for binary search.
Binary Search : In computer science, a binary search or half-interval search algorithm finds the position of a target value within a sorted array. The binary search algorithm can be classified as a dichotomies divide-and-conquer search algorithm and executes in logarithmic time.

Step by step example :

Sample Solution:

Python Code:

def binary_search(item_list,item):
	first = 0
	last = len(item_list)-1
	found = False
	while( first<=last and not found):
		mid = (first + last)//2
		if item_list[mid] == item :
			found = True
		else:
			if item < item_list[mid]:
				last = mid - 1
			else:
				first = mid + 1	
	return found
	
print(binary_search([1,2,3,5,8], 6))
print(binary_search([1,2,3,5,8], 5))

Sample Output:

False                                                                                                         
True

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to implement a binary search that returns the index of the target element if found, otherwise returns -1.
Write a Python program to perform binary search on a sorted list of strings and output the position of a given string.
Write a Python function to implement recursive binary search and count the number of comparisons made during the search.
Write a Python program that uses binary search to determine if a target value exists in a sorted list of floating-point numbers with a tolerance for rounding errors.

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Next: Write a Python program for sequential search.

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