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Python: Get the difference between two given lists, after applying the provided function to each list element of both

Python List: Exercise - 222 with Solution

Write a Python program to get the difference between two given lists, after applying the provided function to each list element of both.

  • Create a set, using map() to apply fn to each element in b.
  • Use a list comprehension in combination with fn on a to only keep values not contained in the previously created set, _b.

Sample Solution:

Python Code:

def difference_by(a, b, fn):
  _b = set(map(fn, b))
  return [item for item in a if fn(item) not in _b]
from math import floor
print(difference_by([2.1, 1.2], [2.3, 3.4], floor)) 
print(difference_by([{ 'x': 2 }, { 'x': 1 }], [{ 'x': 1 }], lambda v : v['x']))

Sample Output:

[1.2]
[{'x': 2}]

Flowchart:

Flowchart: Get the difference between two given lists, after applying the provided function to each list element of both.

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Python: Tips of the Day

Floor Division:

When we speak of division we normally mean (/) float division operator, this will give a precise result in float format with decimals.

For a rounded integer result there is (//) floor division operator in Python. Floor division will only give integer results that are round numbers.

print(1000 // 300)
print(1000 / 300)

Output:

3
3.3333333333333335