How to save a NumPy array to a CSV File and verify contents?

NumPy: Interoperability Exercise-14 with Solution

Write a NumPy program to save a NumPy array to a CSV file and verify the contents by reading the file.

Sample Solution:

Python Code:

import numpy as np
import pandas as pd

# Create a NumPy array
array = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]])

# Save the NumPy array to a CSV file
np.savetxt('array.csv', array, delimiter=',')

# Read the CSV file to verify contents
verified_array = np.loadtxt('array.csv', delimiter=',')

# Print the original NumPy array
print("Original NumPy Array:")
print(array)
print(type(array))
# Print the verified NumPy array read from the CSV file
print("\nVerified NumPy Array from CSV File:")
print(verified_array)
print(type(verified_array))

Output:

Original NumPy Array:
[[1 2 3]
 [4 5 6]
 [7 8 9]]
<class 'numpy.ndarray'>

Verified NumPy Array from CSV File:
[[1. 2. 3.]
 [4. 5. 6.]
 [7. 8. 9.]]
<class 'numpy.ndarray'>

Explanation:

• Import NumPy and Pandas Libraries: Import the NumPy and Pandas libraries to work with arrays and data files.
• Create NumPy Array: Define a NumPy array with some example data.
• Save NumPy Array to CSV File: Use np.savetxt() to save the NumPy array to a CSV file named 'array.csv', specifying the delimiter as a comma.
• Read CSV File to Verify Contents: Use np.loadtxt() to read the contents of the CSV file back into a NumPy array, specifying the delimiter as a comma.
• Print Original NumPy Array: Output the original NumPy array to compare with the verified array.
• Print Verified NumPy Array: Output the NumPy array read from the CSV file to ensure the data was saved and retrieved accurately.

Python-Numpy Code Editor:

Have another way to solve this solution? Contribute your code (and comments) through Disqus.

Previous: How to convert a Pandas DataFrame to a NumPy array and back?
Next: How to read a CSV file into a NumPy array and print it?