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Python: Return every element that exists in any of the two given lists once, after applying function to each element of both

Python List: Exercise - 228 with Solution

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.

  • Create a set by applying fn to each element in x.
  • Use a list comprehension in combination with fn on y to only keep values not contained in the previously created set, _x.
  • Finally, create a set from the previous result and x and transform it into a list.

Sample Solution:

Python Code:

def union_by_el(x, y, fn):
  _x = set(map(fn, x))
  return list(set(x + [item for item in y if fn(item) not in _x])) 
from math import floor
print(union_by_el([4.1], [2.2, 4.3], floor))

Sample Output:

[2.2, 4.1]

Flowchart:

Flowchart: Return every element that exists in any of the two given lists once, after applying function to each element of both.

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Previous: Write a Python program to get the symmetric difference between two lists, after applying the provided function to each list element of both.
Next: Write a Python program to find the index of the first element in the given list that satisfies the provided testing function.

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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