In this article, we will learn about how to write python program to swap two variables without using third variable.

Getting Started

The task is to swap two variables a and b in python without using any other variable.

Let’s say a = 5 and b = 7, then output should be a = 7 and b = 5.

There are multiple ways to achieve above tasks.

1. Using Tuple Packing and Unpacking
2. Using XOR bitwise operation
3. Using Multiplication and Division Operation
4. Using Bitwise Operation

1. Using Tuple Packing and Unpacking

Python provides the simplest way, i.e. Tuple Packing and Unpacking, to swap two variables without using third variable as shown below –

num1 = 5
num2 = 10
print("Before swap: num1 =", num1, "num2 =", num2)
num1, num2 = num2, num1
print("After swap: num1 =", num1, "num2 =", num2)

Here,

• Statement num1, num2 = num2, num1 does the actual swapping process. Rest of the lines in above code example are just to show the output.

Output:

Before swap: num1 = 5 num2 = 10
After swap: num1 = 10 num2 = 5

2. Using XOR bitwise operation

We can also use XOR bitwise operation to write python program to swap two variables without using third variable as shown below –

a = int(input("Enter the value of a: "))
b = int(input("Enter the value of b: "))

# Swapping without using a third variable
a = a ^ b
b = a ^ b
a = a ^ b

# Output swapped values
print("After swapping:")
print("a =", a)
print("b =", b)

Here,

• We have used XOR operator, i.e. ^, for our swap operation.

Output:

Enter the value of a: 5
Enter the value of b: 10
After swapping:
a = 10
b = 5

3. Using Multiplication and Division Operation

We can also use multiplication and division operation to swap two variables without using third variable in python as shown below –

a = 10
b = 20

# Print the values before swapping
print("Before swapping:")
print("Value of a:", a, "and b:", b)

# Swapping without using a third variable
a = a * b  # Multiply a by b. Then, assign the result to a
b = a / b  # Divide a (i.e now, it is a*b) by b. Then, assign the result to b
a = a / b  # Divide a by b. Then, assign the result to a

# Print the values after swapping
print("After swapping:")
print("Value of a:", a, "and b:", b)

Here,

• We have used multiplication and division only to swap two variables in python.

Output:

Before swapping:
Value of a: 10 and b: 20
After swapping:
Value of a: 20.0 and b: 10.0

4. Using Bitwise Operation

We can also use bitwise operation to swap variables without using third variable and print them in python as shown below –

a = 5
b = 10

print("Before swapping:")
print("Value of a:", a, "and b:", b)

# Swapping without using a third variable using bitwise operations
a = (a & b) + (a | b)  # a = (a AND b) + (a OR b)
b = a + (~b) + 1      # b = a + (~b) + 1 (two's complement)
a = a + (~b) + 1      # a = a + (~b) + 1 (two's complement)

print("After swapping:")
print("Value of a:", a, "and b:", b)

Here,

• We are using two’s complement feature and swapping the variables.

Output:

Before swapping:
Value of a: 5 and b: 10
After swapping:
Value of a: 10 and b: 5

We have also covered many other ways to swap two variables in python. You can have a look at them if you want. Learn more about python at official site.