# Lambda

Sun 25 January 2015

Filed under Python

## Lambdas

First: What is 'lambda'?

In very short, lambda is a one-line, mini function. So we just include the short code directly into that line of code instead of writing out a separate function for it. If that mini function would be used in several places in the code, then it still might pay to write a function for it.

For example: if we have to double a digit. Instead of writing a function to do that, we might write a quick lambda.

The Syntax

`(lambda a: a *2)(6)`

• The lambda expression should be in parentheses `()`.

• Starts off with the word `lambda`

• And then the variable name, in this case `a`. There could be more than 1 variable.

• And the colon `:`

• And then the quick little code. In this case `a * 2`. The variable multiplied by 2.

• And lastly an argument for this little lambda function. In this case `(6)`. In its own parentheses. This is how we call the lambda function.

Another way to write a lambda

```c = lambda a: a* 2
c(2)
```

Here we are assigning the lambda function to `c` and then calling `c(2)`. This sort of defeats the purpose. But it still saves some coding since you don't have to `def` or `return`.

A few more examples:

`(lambda x: x <10)(11)`

This lambda checks if `11` is less than `10`. And in this case returns `False`.

`(lambda x: x %2)(8)`

This lambda checks if `8` is evenly divisible by 2. And in this case returns `True`.

`(lambda x, y: x < y)(6, 7)`

This lambda uses 2 variables - `x` and `y`. It compares if `x` is less than `y`. It compares if `6 < 7` and in this case returns `True`.

Lambdas get even cooler

Lambdas can be used with `map`, `reduce` and `filter`. Coming soon.