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Python: Extract a specified column from a given nested list

Python List: Exercise - 108 with Solution

Write a Python program to extract a specified column from a given nested list.

Sample Solution:

Python Code:

def remove_column(nums, n):
   result = [i.pop(n) for i in nums]
   return result 

list1 = [[1, 2, 3], [2, 4, 5], [1, 1, 1]]
n = 0
print("Original Nested list:")
print(list1)
print("Extract 1st column:")
print(remove_column(list1, n))

list2 = [[1, 2, 3], [-2, 4, -5], [1, -1, 1]]
n = 2
print("\nOriginal Nested list:")
print(list2)
print("Extract 3rd column:")
print(remove_column(list2, n))

Sample Output:

Original Nested list:
[[1, 2, 3], [2, 4, 5], [1, 1, 1]]
Extract 1st column:
[1, 2, 1]

Original Nested list:
[[1, 2, 3], [-2, 4, -5], [1, -1, 1]]
Extract 3rd column:
[3, -5, 1]

Pictorial Presentation:

Python List: Extract a specified column from a given nested list.

Flowchart:

Flowchart: Extract a specified column from a given nested list.

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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