Python Program to Find Whether a Number is a Power of Two

This is a Python program to find whether a number is a power of two.

A number is given. The problem is to determine whether the number is a power of two.

1. The function is_power_of_two is defined.
2. It takes a number n as argument and returns True if the number is a power of two.
3. If n is not positive, False is returned.
4. If n is positive, then n & (n – 1) is calculated.
5. The above expression equals n with its rightmost set bit cleared. That is, the rightmost 1 in the binary representation of n is made 0.
6. All powers of two have only one set bit in their binary representation and all numbers with only one set bit is a power of two.
7. Thus n & (n – 1) will equal zero iff n is a power of two.
8. This is used to determine if n is a power of two if n is positive.

Here is the source code of a Python program to find whether a number is a power of two. The program output is shown below.

def is_power_of_two(n):
    """Return True if n is a power of two."""
    if n <= 0:
        return False
    else:
        return n & (n - 1) == 0
 
 
n = int(input('Enter a number: '))
 
if is_power_of_two(n):
    print('{} is a power of two.'.format(n))
else:
    print('{} is not a power of two.'.format(n))

1. The user is prompted to enter a number.
2. is_power_of_two is called on the number.
3. If the return value is True, the number is a power of two.

Case 1:
Enter a number: 5
5 is not a power of two.
 
Case 2:
Enter a number: 0
0 is not a power of two.
 
Case 3:
Enter a number: 8
8 is a power of two.

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