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Python Bisect: Find the first occurrence of a given number in a sorted list using Binary Search

Python Bisect: Exercise-4 with Solution

Write a Python program to find the first occurrence of a given number in a sorted list using Binary Search (bisect).

Sample Solution:

Python Code:

from bisect import bisect_left   
def Binary_Search(a, x): 
    i = bisect_left(a, x) 
    if i != len(a) and a[i] == x: 
        return i 
    else: 
        return -1

nums = [1, 2, 3, 4, 8, 8, 10, 12] 
x = 8 
num_position = Binary_Search(nums, x) 
if num_position == -1: 
    print(x, "is not present.") 
else: 
    print("First occurrence of", x, "is present at index", num_position)

Sample Output:

First occurrence of 8 is present at index 4

Flowchart:

Flowchart: Find the first occurrence of a given number in a sorted list using Binary Search.

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Previous: Write a Python program to insert items into a list in sorted order.

Next: Write a Python program to find the index position of the largest value smaller than a given number in a sorted list using Binary Search (bisect).

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Python: Tips of the Day

How to make a chain of function decorators?

from functools import wraps

def makebold(fn):
    @wraps(fn)
    def wrapped(*args, **kwargs):
        return "<b>" + fn(*args, **kwargs) + "</b>"
    return wrapped

def makeitalic(fn):
    @wraps(fn)
    def wrapped(*args, **kwargs):
        return "<i>" + fn(*args, **kwargs) + "</i>"
    return wrapped

@makebold
@makeitalic
def hello():
    return "hello world"

@makebold
@makeitalic
def log(s):
    return s

print hello()        # returns "<b><i>hello world</i></b>"
print hello.__name__ # with functools.wraps() this returns "hello"
print log('hello')   # returns "<b><i>hello</i></b>"

Ref: https://bit.ly/3cVz5iw