day-11

File Handling

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Files are a fundamental part of software development. They are used to store and retrieve data. In this lesson, we'll explore how to interact with files in Python.

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File Handling Basics

File handling involves two essential operations: reading data from files and writing data to files. Reading allows us to access existing data, while writing enables us to store new data.

Reading Files

To read data from a file, we open the file, access its contents, and then close it. Properly closing a file is important to free up system resources.

Example Code:

# Open a file for reading
with open('sample.txt', 'r') as file:
    content = file.read()
    print(content)

In this example, we open a file ('sample.txt') in read mode ('r') using the with statement. The read() method is then used to read the entire content of the file into the variable content. Finally, we print the content.

Additional Example - Reading Lines:

# Open a file for reading
with open('sample.txt', 'r') as file:
    lines = file.readlines()
    for line in lines:
        print(line.strip())  # Use strip() to remove newline characters

This example reads the file line by line using readlines(). The strip() method is applied to remove newline characters from each line before printing.

Writing to Files

Writing to files is essential for storing data. We open a file for writing, add data to it, and then close it. Modes like "w" and "a" determine whether data is overwritten or appended.

Example Code:

# Open a file for writing
with open('output.txt', 'w') as file:
    file.write("Hello, World!\n")

Here, we open a file ('output.txt') in write mode ('w') using the with statement. We then use the write() method to add the text "Hello, World!" to the file. The '\n' represents a newline character.

Additional Example - Appending to a File:

# Open a file for appending
with open('output.txt', 'a') as file:
    file.write("Appending more text!\n")

This example opens the same file in append mode ('a') and appends the text "Appending more text!\n" to the existing content.

File Handling Best Practices

Properly closing files is a best practice to prevent resource leaks. The with statement ensures automatic file closure, enhancing code robustness.

The with statement automatically takes care of closing the file when the code block is exited, even if an exception occurs. This practice ensures that system resources are efficiently managed.

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Additional Resources:

• File Handling W3Schools

• Python Tutorial: File Objects - Reading and Writing to Files

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CHALLENGE TIME!!!

In a text file, provide students with a list of names, one name per line. Ask them to create a Python program that reads the names, sorts them alphabetically, and writes the sorted names back to the file.

Hint:

• You can read the names from the file using the .readlines() method. This function reads each line in the file and returns a list of lines, making it easier to work with line-based data. To write the sorted names back to the file, consider using the .writelines() method, which allows you to write a list of strings back to the file.