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

Python List: Exercise - 227 with Solution

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

  • Create a set by applying fn to each element in every list.
  • Use a list comprehension in combination with fn on each of them to only keep values not contained in the previously created set of the other.

Sample Solution:

Python Code:

def symmetric_difference_by(a, b, fn):
  (_a, _b) = (set(map(fn, a)), set(map(fn, b)))
  return [item for item in a if fn(item) not in _b] + [item
          for item in b if fn(item) not in _a]
from math import floor
print(symmetric_difference_by([2.1, 1.2], [2.3, 3.4], floor))

Sample Output:

[1.2, 3.4]

Flowchart:

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

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Previous: Write a Python program to get a list of elements that exist in both lists, after applying the provided function to each list element of both.
Next: Write a Python program to get every element that exists in any of the two given lists once, after applying the provided function to each 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