---
title: min_by
tags: math,list,function,beginner
---

Returns the minimum value of a list, after mapping each element to a value using the provided function.

Use `map()` with `fn` to map each element to a value using the provided function, use `min()` to return the minimum value.

```py
def min_by(lst, fn):
  return min(map(fn,lst))
```

```py
min_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda v : v['n']) # 2
```
