File Handling Fundamentals: A Comprehensive Guide for IGCSE Computer Science 0478

 

File Handling (Section 8.3)

Table of Contents

1. Introduction to File Handling
   • 1.1 Purpose of Storing Data in a File
2. Opening and Closing Files
   • 2.1 Opening a File
   • 2.2 Closing a File
3. Reading and Writing Files
   • 3.1 Reading Data from a File
     • 3.1.1 Reading Single Items of Data
     • 3.1.2 Reading a Line of Text
   • 3.2 Writing Data to a File
     • 3.2.1 Writing Single Items of Data
     • 3.2.2 Writing a Line of Text
4. Summary

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1. Introduction to File Handling

1.1 Purpose of Storing Data in a File

File handling is an essential concept in programming that allows data to be stored persistently, meaning it remains available even after the program has finished running. The purposes of storing data in a file include:

• Persistence: Unlike variables that lose their values when a program ends, files maintain data for future access.
• Data Management: Files allow for organized storage of large amounts of data that can be easily accessed and modified.
• Sharing Data: Files enable data sharing between different programs or users.
• Backup and Recovery: Files provide a means to back up important data, ensuring it can be restored in case of loss.

2. Opening and Closing Files

2.1 Opening a File

To interact with a file, a program must first open it. The process of opening a file involves specifying the file's name and the mode in which it will be used. Common modes include:

• Read Mode ('r'): Opens the file for reading. An error occurs if the file does not exist.
• Write Mode ('w'): Opens the file for writing. If the file exists, it is overwritten; if not, a new file is created.
• Append Mode ('a'): Opens the file for adding new data. Existing data is preserved.

In Python, opening a file can be done using the open() function:

python
file = open('filename.txt', 'r')  # Opens file for reading

2.2 Closing a File

After completing file operations, it is crucial to close the file to free system resources and ensure all data is saved. This is done using the close() method:

python
file.close()  # Closes the opened file

3. Reading and Writing Files

3.1 Reading Data from a File

Reading data from a file allows a program to retrieve information stored previously.

3.1.1 Reading Single Items of Data

To read a single item from a file, the read() method can be used. It reads a specified number of characters from the file:

python
file = open('data.txt', 'r')
data = file.read(10)  # Reads the first 10 characters
file.close()

3.1.2 Reading a Line of Text

To read an entire line from a file, the readline() method is utilized. This reads the next line of the file:

python
file = open('data.txt', 'r')
line = file.readline()  # Reads the first line of the file
file.close()

3.2 Writing Data to a File

Writing data to a file allows programs to save new information.

3.2.1 Writing Single Items of Data

To write data to a file, the write() method is used. This can be done in either write or append mode:

python
file = open('data.txt', 'w')
file.write('Hello, World!')  # Writes a string to the file
file.close()

3.2.2 Writing a Line of Text

To write a complete line of text followed by a newline character, the writelines() method can be used or simply include \n:

python
file = open('data.txt', 'a')  # Opens in append mode
file.write('This is a new line.\n')  # Writes a new line to the file
file.close()

4. Summary

File handling is a critical aspect of programming, enabling data persistence, management, sharing, and backup. Understanding how to open, close, read, and write files is essential for effective programming. By using methods like open(), read(), write(), and close(), candidates can manipulate files to achieve their data storage needs efficiently.