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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

Flowchart:

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

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Previous: Write a Python program to convert a given list of dictionaries into a list of values corresponding to the specified key.
Next: Write a Python program to find the value of the first element in the given list that satisfies the provided testing function.

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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]]