Python Exception Handling and File Modes Explained

What is an Exception?

Answer: An exception in Python is an error that occurs during program execution, disrupting the normal flow of instructions. Instead of crashing, the program can "catch" the exception and handle it gracefully using try and except blocks. Common exceptions include ZeroDivisionError, IndexError, and FileNotFoundError. You can also define custom exceptions. The finally block can be used for cleanup actions, ensuring certain code runs regardless of whether an exception was raised.

Different Modes of Opening a File

Answer: Different Modes of Opening a File

1. Read Mode ('r')

• Purpose: Opens a file for reading.
• Behavior:
  • The file pointer is placed at the beginning of the file.
  • If the file does not exist, a FileNotFoundError is raised.
• Example:

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

2. Write Mode ('w')

• Purpose: Opens a file for writing.
• Behavior:
  • If the file already exists, its contents are truncated (i.e., deleted).
  • If the file does not exist, a new file is created.
• Example:

  file = open('example.txt', 'w')
  file.write("This will overwrite the existing content.")
  file.close()

Exception Handling in Detail

Answer: Exception handling is a programming technique used to manage and respond to runtime errors, allowing a program to continue functioning even when an unexpected situation occurs. It provides a way to handle errors gracefully without crashing the program and to ensure that the program behaves in a predictable and controlled manner.

Key Concepts of Exception Handling in Python

1. The try Block

• The try block is where you place the code that might raise an exception. If the code runs without any issues, the program skips the except blocks. However, if an exception occurs, Python stops executing the code within the try block and looks for an except block to handle the exception.

2. The except Block

• The except block is used to handle the exception that was raised in the try block. You can specify different except blocks for different types of exceptions or use a general except block to catch any exception.