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

Last update on April 19 2025 12:57:48 (UTC/GMT +8 hours)

Average Mapped Values

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:

# Define a function 'average_by' that takes a list 'lst' and an optional function 'fn' as input.
def average_by(lst, fn=lambda x: x):
    # Calculate the average of the values in the list 'lst' by performing the following steps:
    # 1. Use the 'map' function to apply the function 'fn' to each element of the list 'lst'.
    # 2. Use 'sum' to calculate the sum of the mapped values, starting with a floating-point 0.0.
    # 3. Divide the sum by the length of the list 'lst' to compute the average.
    return sum(map(fn, lst), 0.0) / len(lst)

# Call the 'average_by' function with a list of dictionaries and a lambda function to extract the 'n' key's value.
# Print the result, which is the average of the 'n' values.
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:

For more Practice: Solve these Related Problems:

Write a Python program to calculate the average of a list after mapping each string element to its length.
Write a Python program to compute the average of a list of numbers after normalizing them to a 0-1 scale via a provided function.
Write a Python program to calculate the average of values obtained by mapping each element to its square root.
Write a Python program to compute the average of a list after applying a logarithmic transformation to each element.

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