# How to Swap Two Variables in One Line Python?

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Problem: Given two variables `a` and `b`. Use a single line of Python code to swap the variables to assign the value of `a` to `b` and the value of `b` to `a`.

Example: Say, you have to integers `a=21` and `b=42`. You want to swap the variables so that `a=42` and `b=21`.

```a = 21
b = 42
# SWAP MAGIC HERE
print(a, b)
# 42 21```

How to swap to variables as a Python one-liner?

Let’s dive into the best ways to swap integers!

## Swap Integers

To swap two variables a and b, use the multiple assignment expression `a, b = b, a` that assigns the value of `a` to `b` and the value of `b` to `a`.

```a = 21
b = 42

# Swap One-Liner
a, b = b, a

# Print the result to the shell
print(a, b)
# 42 21
```

## Explanation

The Python interpreter evaluates every expression from left to right. Python realizes that in order to assign the value to the variables, it must first evaluate the right-hand-side of the equation. So, here are the steps it takes to determine the result of the line `a, b = b, a`:

• The right side `b, a` is short for `(b, a)` and, thus, it creates a tuple in memory with two values. The first tuple value is the object to which the variable `b` points in memory (here: `42`). The second tuple value is the object to which the variable `a` points in memory (here: `21`). In our case, the memory now contains a new tuple object `(42, 21)`.
• Python now assigns this tuple to the list of variables defined on the left-hand side of the equation (here: `a, b = ...`). The variable name `a` now points to the first tuple value (here: `42`). The variable name `b` now points to the second tuple value (here: `21`).
• This way, the tuple is unpacked to the variables on the left-hand side. Variables `a` and `b` have been swapped.

Do It Yourself: You can see this code and the memory in action in the interactive memory visualizer:

Click “Next” to view how the memory objects unfold.

Does this also work to swap other objects like lists or strings?

## How to Swap Lists, Tuples, and Other Objects

Let’s try out in our interactive code shell:

Exercise: Print the result of the variables `a` and `b` before and after swapping. Can you swap any object using Python’s multiple assignment feature?

You can see this code and the memory in action in the interactive memory visualizer:

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