File Handling in Python How to read from and write to files in Python, and practical use cases like logs or saving results.

 File handling in Python is essential for reading from and writing to files, which is useful for various applications such as logging, saving results, or processing data. Below, I’ll outline the basic methods for file handling, along with practical use cases.

Reading from Files

To read from a file, you can use the built-in open() function along with methods like .read(), .readline(), or .readlines().

Example: Reading a File

# Open a file in read mode

with open('example.txt', 'r') as file:

    content = file.read()  # Reads the entire file

    print(content)

Writing to Files

To write to a file, you can also use the open() function, but in write ('w') or append ('a') mode.

Example: Writing to a File

# Open a file in write mode

with open('output.txt', 'w') as file:

    file.write("Hello, World!\n")  # Writes a line to the file

Practical Use Cases

1. Logging:

• Use a log file to record events or errors in your application.
• Example:

import logging

logging.basicConfig(filename='app.log', level=logging.INFO)

logging.info('This is an info message.')

2.Saving Results:

• After performing calculations, you can save results for future reference.
• Example:

results = [1, 2, 3, 4, 5]

with open('results.txt', 'w') as file:

    for result in results:

        file.write(f"{result}\n")

3.Data Processing:

• Read data from a file, process it, and write the results back.
• Example:

with open('data.txt', 'r') as infile, open('processed_data.txt', 'w') as outfile:

    for line in infile:

        processed_line = line.strip().upper()  # Example processing

        outfile.write(processed_line + '\n')

Summary

• Use open() to access files, specifying the mode ('r', 'w', 'a').
• Use context managers (with statement) to ensure files are properly closed.
• Practical applications include logging, saving results, and data processing.