Start of main content## Recommended snippets

Calculates the average of a list, after mapping each element to a value using the provided function.

- Use
`map()`

to map each element to the value returned by`fn`

. - Use
`sum()`

to sum all of the mapped values, divide by`len(lst)`

. - Omit the last argument,
`fn`

, to use the default identity function.

```
def average_by(lst, fn = lambda x: x):
return sum(map(fn, lst), 0.0) / len(lst)
```

```
average_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda x: x['n'])
# 5.0
```

### Sum list based on function

Python, Math

Calculates the sum of a list, after mapping each element to a value using the provided function.

### Max list value based on function

Python, Math

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

### Min list value based on function

Python, Math

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