# What are lambda expressions in Python?

### Patrick Hanford ・1 min read

# What are lambda expressions?

lambda expressions in Python are best described as ** single-use anonymous functions**. What I mean by this, can be explained with a quick example.

```
[1,2,3,4,5]
```

I have this list of numbers that I want to square (multiply by itself). I could create a function like so.

```
def square(number):
return number*number
```

This works fine, but what if you only need to do this one time? It would be a little cumbersome to have a function dedicated to this pretty menial task. We can use a lambda express for this instead.

```
lambda number: number*number
```

So you can see what's happening by referencing the above function next to our lambda expression. We declare `lambda`

so the interpreter knows this is a lambda express. The first item is then the parameter which replaces the `number`

argument in the `square()`

function. Next is the actual result of the expression, `number*number`

.

Here's an example using `map()`

to get the squared result of each number in our list.

```
list(map(lambda number: number*number, numbers))
> [1,4,9,16,25]
```

I hope this is a good example to help you grasp lambda expressions so you can avoid huge pages of disposable functions!

don't forget to pass the numbers to the map()

`list(map(lambda number: number*number, numbers))`

Ah ha, good catch!

Thank you, this was a good refresher from what I learned earlier in the year