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NumPy: Test whether a given 2D array has null columns or not


Check if a 2D array has null columns.

Write a NumPy program to test whether a given 2D array has null columns or not.

Pictorial Presentation:

Python NumPy: Test whether a given 2D array has null columns or not

Sample Solution:

Python Code:

# Importing the NumPy library
import numpy as np

# Displaying the message indicating the original array
print("Original array:")

# Generating a random integer array of shape (4, 10) with values ranging from 0 to 2
nums = np.random.randint(0, 3, (4, 10))

# Displaying the original array
print(nums)

# Checking if the array has any null columns and displaying the result
print("\nTest whether the said array has null columns or not:")
print((~nums.any(axis=0)).any()) 

Sample Output:

Original array:
[[1 2 1 1 1 2 1 1 2 0]
 [1 1 0 0 0 0 2 1 2 0]
 [0 0 2 1 0 2 2 2 2 2]
 [1 1 1 2 0 0 0 0 1 2]]

Test whether the said array has null columns or not:
False

Explanation:

In the above exercise -

nums = np.random.randint(0,3,(4,10)): Generates a 4x10 NumPy array nums with random integers from the range [0, 3).

print((~nums.any(axis=0)).any()):

In the above code -

  • nums.any(axis=0): Returns a boolean array of shape (10,) with True at positions where there is at least one non-zero element in the corresponding column of nums, and False otherwise. The axis=0 parameter specifies that the operation should be performed along the columns.
  • ~nums.any(axis=0): Inverts the boolean values in the array from step 2 using the bitwise NOT operator ~. Now, True indicates that a column has all zeros, and False indicates that there is at least one non-zero element in the column.
  • (~nums.any(axis=0)).any(): Checks if there is at least one True value in the boolean array from step 3, i.e., if there is any column in nums with all zeros.
  • print((~nums.any(axis=0)).any()): Finally print() function prints the result from step 4. If it prints True, there is at least one column with all zeros; otherwise, no such column exists.

For more Practice: Solve these Related Problems:

  • Write a NumPy program to check if any column in a 2D array consists entirely of zeros using np.all and axis=0.
  • Create a function that returns a boolean for each column indicating whether it is null (all zeros).
  • Implement a solution that compares the sum of each column to zero to detect null columns.
  • Test the function on arrays with sparse data to validate that it accurately identifies empty columns.

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