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

Last update on April 29 2025 13:00:13 (UTC/GMT +8 hours)

14. Array to CSV Conversion

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.

For more Practice: Solve these Related Problems:

Write a Numpy program to save a multidimensional NumPy array to a CSV file with a custom delimiter and then verify the shape upon reloading.
Write a Numpy program to export a structured NumPy array to CSV and then read it back while preserving column data types.
Write a Numpy program to write a NumPy array to a CSV file with headers and footers, then validate the written content by parsing the file.
Write a Numpy program to save a large NumPy array to CSV in chunks and then combine the chunks back into a single array for verification.

Go to:

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