7 File Handling Explained

Key Concepts

File handling in Python involves several key concepts:

• Opening Files
• Reading Files
• Writing to Files
• Closing Files
• File Modes
• Handling Exceptions

1. Opening Files

To work with a file, you first need to open it using the open() function. This function returns a file object, which you can then use to read from or write to the file.

Example:

file = open('example.txt', 'r')
    

Analogy: Think of opening a file as unlocking a door to access the contents inside.

2. Reading Files

Once a file is opened, you can read its contents using various methods such as read(), readline(), and readlines().

Example:

file = open('example.txt', 'r')
content = file.read()
print(content)
file.close()
    

Analogy: Reading a file is like reading a book, where you extract information line by line or all at once.

3. Writing to Files

You can write data to a file using the write() method. If the file does not exist, it will be created. If it does exist, the content will be overwritten unless you specify append mode.

Example:

file = open('example.txt', 'w')
file.write('Hello, World!')
file.close()
    

Analogy: Writing to a file is like writing a letter, where you put your thoughts into words and save them for later.

4. Closing Files

After you are done with a file, it is important to close it using the close() method. This frees up system resources and ensures changes are saved.

Example:

file = open('example.txt', 'r')
content = file.read()
file.close()
    

Analogy: Closing a file is like putting away a book after you have finished reading it.

5. File Modes

When opening a file, you can specify the mode in which the file should be opened. Common modes include:

• 'r': Read mode (default)
• 'w': Write mode (creates a new file or truncates an existing file)
• 'a': Append mode (appends to the end of the file)
• 'b': Binary mode (used for non-text files)

Example:

file = open('example.txt', 'a')
file.write('\nAppended text')
file.close()
    

Analogy: File modes are like different ways to use a book, whether you are reading, writing, or adding to it.

6. Handling Exceptions

When working with files, it is important to handle exceptions that may occur, such as file not found errors. You can use a try-except block to handle these exceptions gracefully.

Example:

try:
    file = open('nonexistent.txt', 'r')
    content = file.read()
    file.close()
except FileNotFoundError:
    print('The file does not exist.')
    

Analogy: Handling exceptions is like having a backup plan in case something goes wrong, ensuring your program does not crash.

Putting It All Together

By understanding and using file handling effectively, you can manage data persistence and interact with files in various ways. This is crucial for building robust and scalable applications.

Example:

try:
    file = open('example.txt', 'a')
    file.write('\nNew line added')
    file.close()
    
    file = open('example.txt', 'r')
    content = file.read()
    print(content)
    file.close()
except FileNotFoundError:
    print('The file does not exist.')