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

Last update on April 19 2025 13:00:57 (UTC/GMT +8 hours)

Sum Mapped Values in List

Write a Python program to calculate the sum 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 sum() to return the sum of the values.

Sample Solution:

Python Code:

# Define a function 'sum_by' that takes a list 'lst' and a function 'fn'.
# It calculates the sum of the values obtained by applying 'fn' to each element in the list.
def sum_by(lst, fn):
    return sum(map(fn, lst))

# Call the 'sum_by' function with a list of dictionaries and a lambda function.
# The lambda function extracts the 'n' value from each dictionary.
# The function returns the sum of all 'n' values from the list of dictionaries.
print(sum_by([{ 'n': 4 }, { 'n': 2 }, { 'n': 8 }, { 'n': 6 }], lambda v : v['n']))

Sample Output:

Flowchart:

For more Practice: Solve these Related Problems:

Write a Python program to calculate the sum of a list after applying a function that doubles each element.
Write a Python program to compute the sum of mapped values in a list where each element is transformed to its square before summation.
Write a Python program to sum a list after mapping each element to its integer representation from a string, handling conversion errors gracefully.
Write a Python program to calculate the sum and then the average of a list after applying a logarithmic transformation to each element.

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