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NumPy: Sort an given array by the nth column

NumPy Sorting and Searching: Exercise-9 with Solution

Write a NumPy program to sort an given array by the nth column.

Sample Solution:

Python Code:

import numpy as np
print("Original array:\n")
nums = np.random.randint(0,10,(3,3))
print(nums)
print("\nSort the said array by the nth column: ")
print(nums[nums[:,1].argsort()])

Sample Output:

Original array:

[[1 5 0]
 [3 2 5]
 [8 7 6]]

Sort the said array by the nth column: 
[[3 2 5]
 [1 5 0]
 [8 7 6]]

Python-Numpy Code Editor:

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Previous: Write a NumPy program to sort the specified number of elements from beginning of a given array.
Next: Sorting and Searching Exercises Home.

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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