How to write a structured NumPy array to a CSV file with proper formatting?

Last update on April 29 2025 12:54:25 (UTC/GMT +8 hours)

4. Structured Array CSV Write

Write a structured NumPy array to a CSV file, ensuring proper formatting of different data types.

Sample Solution:

Python Code:

import numpy as np
import csv

# Create a structured NumPy array with different data types
data = np.array([
    (1, 'Zayden Jer', 86.5),
    (2, 'Luna Marci', 90.0),
    (3, 'Kord Shane', 88.0),
    (4, 'Coeus Zora', 91.5)
], dtype=[('ID', 'i4'), ('Name', 'U10'), ('Score', 'f4')])

# Define the path to the output CSV file
csv_file_path = 'structured_output.csv'

# Write the structured NumPy array to a CSV file
with open(csv_file_path, 'w', newline='') as csvfile:
    writer = csv.writer(csvfile, delimiter=',')
    # Write the header
    writer.writerow(data.dtype.names)
    # Write the data rows
    for row in data:
        writer.writerow(row)

# Print a message indicating the CSV file has been written
print(f"Data has been written to {csv_file_path}")

Output:

Data has been written to structured_output.csv

Content of  structured_output.csv
ID,Name,Score
1,Zayden Jer,86.5
2,Luna Marci,90.0
3,Kord Shane,88.0
4,Coeus Zora,91.5

Explanation:

Import NumPy and CSV Libraries: Import the NumPy and CSV libraries to handle structured arrays and writing to CSV files.
Create a Structured NumPy Array: Define a structured NumPy array with different data types (integers, strings, and floats) for each column.
Define CSV File Path: Specify the path where the output CSV file will be saved.
Open CSV File for Writing: Open the CSV file in write mode using open(). Create a CSV writer object with the specified delimiter.
Write Header: Use writer.writerow() to write the column names (header) to the CSV file.
Write Data Rows: Iterate through each row of the structured NumPy array and write it to the CSV file using writer.writerow().
Finally output a message indicating that the data has been successfully written to the CSV file.

For more Practice: Solve these Related Problems:

Write a Numpy program to export a structured array with various data types to a CSV file while ensuring correct formatting for each type.
Write a Numpy program to write a structured array to CSV and then re-import it, validating that the data types remain consistent.
Write a Numpy program to format a structured array into CSV with headers and footers, then compare the output with a manual format.
Write a Numpy program to write a structured array to a CSV file and then modify the CSV by adding a new column via external processing.

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