NumPy: Create a 2-dimensional array of size 2 x 3, composed of 4-byte integer elements

Last update on August 29 2025 12:48:41 (UTC/GMT +8 hours)

Count occurrences of sequences in a 2D array.

Create a 2-dimensional array of size 2 x 3, composed of 4-byte integer elements. Write a NumPy program to find the number of occurrences of a sequence in the said array.

Sample Solution:

Python Code:

# Importing NumPy library
import numpy as np

# Creating a NumPy array with specific values and data type (np.int32)
np_array = np.array([[1, 2, 3], [2, 1, 2]], np.int32)

# Printing the original NumPy array and its type
print("Original NumPy array:")
print(np_array)
print("Type: ", type(np_array))

# Printing the sequence to search for in the NumPy array
print("Sequence: 1,2",)

# Counting the number of occurrences of the specified sequence "1, 2" in the array representation
result = repr(np_array).count("1, 2")

# Printing the number of occurrences of the specified sequence in the array
print("Number of occurrences of the said sequence:", result)

Sample Output:

Original Numpy array:
[[1 2 3]
 [2 1 2]]
Type:  <class 'numpy.ndarray'>
Sequence: 1,2
Number of occurrences of the said sequence: 2

Explanation:

np_array = np.array([[1, 2, 3], [2, 1, 2]], np.int32) creates a 2x3 NumPy array with elements of type int32. np_array variable stores the created 2D array.

result = repr(np_array).count("1, 2")

In the above code -

repr(np_array) converts the NumPy array to its string representation. In this case, the string representation would be 'array([[1, 2, 3],\n [2, 1, 2]], dtype=int32)'.
count("1, 2") counts the number of occurrences of the sub-string "1, 2" in the string representation of the NumPy array.
'result' variable stores the count of the sub-string occurrences.

Pictorial Presentation:

NumPy: Create a 2-dimensional array of size 2 x 3, composed of 4-byte integer elements.

For more Practice: Solve these Related Problems:

Write a NumPy program to count how many times a given sub-sequence appears in each row of a 2D array.
Create a function that uses convolution to detect and count the occurrences of a specified sequence.
Implement a solution that slides a window over each row of a 2D array and tallies matches to the target sequence.
Test the sequence counting on arrays with overlapping sequences to ensure accurate counting.

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