46 lines
978 B
Markdown
46 lines
978 B
Markdown
|
---
|
||
|
|
tags:
|
||
|
|
- python
|
||
|
|
- aws-lambda
|
||
|
|
- AWS
|
||
|
|
---
|
||
|
|
|
||
|
|
# Lambdas in Python
|
||
|
|
|
||
|
|
In Python, anonymous functions like arrow-functions in JavaScript (`() => {}`)
|
||
|
|
are immediately invoked and unnamed. They are called lambdas.
|
||
|
|
|
||
|
|
Whilst they are unnamed, just like JS, the value they return can be stored in a
|
||
|
|
variable. They do not require the `return` keyword.
|
||
|
|
|
||
|
|
They are most often used unnamed with the functional methods
|
||
|
|
[map, filter](Map_and_filter_in_Python.md)
|
||
|
|
and reduce.
|
||
|
|
|
||
|
|
Here is the two syntaxes side by side:
|
||
|
|
|
||
|
|
```js
|
||
|
|
// JavaScript
|
||
|
|
|
||
|
|
const double = (x) => x * x;
|
||
|
|
```
|
||
|
|
|
||
|
|
```py
|
||
|
|
# Python
|
||
|
|
|
||
|
|
double = lambda x: x * x
|
||
|
|
```
|
||
|
|
|
||
|
|
Here is a lambda with multiple parameters:
|
||
|
|
|
||
|
|
```py
|
||
|
|
func = lambda x, y, z: x + y + z
|
||
|
|
print(func(2, 3, 4))
|
||
|
|
# 9
|
||
|
|
```
|
||
|
|
|
||
|
|
> Lambdas obviously enshrine functional programming paradigms. Therefore they
|
||
|
|
> should be pure functions, not mutating values or issueing side effects. For
|
||
|
|
> example, it would be improper (though syntactically well-formed) to use a
|
||
|
|
> lambda to `print` something
|