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NumPy: Create a new array from a given array swapping first and last rows

NumPy: Basic Exercise-50 with Solution

Write a NumPy program to create a 4x4 array with random values, now create a new array from the said array swapping first and last rows.

Sample Solution :

Python Code :

import numpy as np
nums = np.arange(16, dtype='int').reshape(-1, 4)
print("Original array:")
print(nums)
print("\nNew array after swapping first and last rows of the said array:")
nums[[0,-1],:]=nums[[-1,0],:]
print(nums)

Sample Output:

Original array:
[[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]
 [12 13 14 15]]

New array after swapping first and last rows of the said array:
[[12 13 14 15]
 [ 4  5  6  7]
 [ 8  9 10 11]
 [ 0  1  2  3]]

Python-Numpy Code Editor:

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Previous: Write a NumPy program to generate a uniform, non-uniform random sample from a given 1-D array with and without replacement.
Next: Write a NumPy program to create a new array of given shape (5,6) and type, filled with zeros.

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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