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Python: Create a list with the unique values filtered out

Python List: Exercise - 224 with Solution

Write a Python program to create a list with the unique values filtered out.

  • Use collections.Counter to get the count of each value in the list.
  • Use a list comprehension to create a list containing only the non-unique values.

Sample Solution:

Python Code:

from collections import Counter
def filter_unique(lst):
  return [item for item, count in Counter(lst).items() if count > 1] 
print(filter_unique([1, 2, 2, 3, 4, 4, 5]))

Sample Output: 

[2, 4]

Flowchart:

Flowchart: Create a list with the unique values filtered out.

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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