﻿ Python: Calculate the average of a given list, after mapping each element to a value using the provided function - w3resource

# Python: Calculate the average of a given list, after mapping each element to a value using the provided function

## Python List: Exercise - 238 with Solution

Write a Python program to calculate the average of a given 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.

Sample Solution:

Python Code:

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

print(average_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda x: x['n']))
print(average_by([{ 'n': 10 }, { 'n': 20 }, { 'n': -30 }, { 'n': 60 }], lambda x: x['n']))
```
```

Sample Output:

```5.0
15.0
```

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## Python: Tips of the Day

Creates a list of elements, grouped based on the position in the original lists:

Example:

```def tips_zip(*args, fill_value=None):
max_length = max([len(lst) for lst in args])
result = []
for i in range(max_length):
result.append([
args[k][i] if i < len(args[k]) else fillvalue for k in range(len(args))
])
return result
print(tips_zip(['a', 'b'], [1, 2], [True, False]))
print(tips_zip(['a'], [1, 2], [True, False]))
print(tips_zip(['a'], [1, 2], [True, False], fill_value = '1'))
```

Output:

```[['a', 1, True], ['b', 2, False]]
[['a', 1, True], [None, 2, False]]
[['a', 1, True], ['1', 2, False]]
```