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]
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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
Find current directory and file's directory:
To get the full path to the directory a Python file is contained in, write this in that file:
import os dir_path = os.path.dirname(os.path.realpath(__file__))
(Note that the incantation above won't work if you've already used os.chdir() to change your current working directory, since the value of the __file__ constant is relative to the current working directory and is not changed by an os.chdir() call.)
To get the current working directory use
import os cwd = os.getcwd()
Documentation references for the modules, constants and functions used above:
- The os and os.path modules.
- The __file__ constant
- os.path.realpath(path) (returns "the canonical path of the specified filename, eliminating any symbolic links encountered in the path")
- os.path.dirname(path) (returns "the directory name of pathname path")
- os.getcwd() (returns "a string representing the current working directory")
- os.chdir(path) ("change the current working directory to path")
Ref: https://bit.ly/3fy0R6m
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