Exception Handling in Python | Chapter 06 Exception Handling Class 12th Computer Science

Name: Exception Handling in Python | Chapter 06 Exception Handling Class 12th Computer Science
Uploaded: 2025-04-11T14:00:40.000Z
Duration: 1 h 48 min

Introduction to Exception Handling in Python

What is an Exception?

An exception refers to a situational error that occurs during the execution of a program, which may not always result in an error message.

Situational errors can cause a program to halt unexpectedly, such as when trying to read data from a non-existent file.

Examples of Exceptions

If a program attempts to access a file that does not exist, it generates an exception despite the rest of the code being correct.

Another example includes printing with a printer that runs out of paper; this situation leads to an interruption in the print job due to an exception.

Internet connectivity issues while fetching data can also trigger exceptions even if the code itself is functioning correctly.

Handling Exceptions

Programmers can handle exceptions using specific keywords in Python: try, except, else, and finally. These are crucial for managing built-in exceptions effectively.

Built-in exceptions are predefined by Python for common situations that might arise during execution, allowing developers to manage them without creating custom solutions.

User-defined Exceptions

Creating Custom Exceptions

Developers can create user-defined exceptions using the raise and assert keywords, enabling tailored handling for unique scenarios within their programs.

Agenda Overview

Topics Covered

The session will cover various topics including:

Introduction to syntax errors and exceptions.

How built-in and user-defined exceptions work.

Detailed exploration of try-except blocks for managing potential errors in code execution.

Exception Management Techniques

Discussion on how multiple exceptions can be managed together.

Explanation of try-except-finally constructs along with user-defined exception generation techniques using raise and assert statements.

Understanding Errors

Types of Errors

Errors encountered during programming can be categorized into:

Syntax Errors: Occur when incorrect code structure is used (e.g., invalid operations).

Runtime Errors: Happen during program execution due to unforeseen circumstances (e.g., accessing undefined variables).

Logical Errors: Result from flawed logic leading to unexpected outcomes despite no syntax or runtime errors being present.

This structured overview provides insights into exception handling concepts essential for effective programming practices in Python, emphasizing both built-in functionalities and custom solutions through user-defined exceptions.

Understanding Runtime Errors and Exceptions in Python

What is a Runtime Error?

A runtime error occurs when the program encounters an unexpected situation while executing, such as incorrect user input. For example, if a user inputs "FIVE" instead of the numeric value 5 for age, it leads to an error.

Types of Errors

Logical errors occur when the logic used in calculations is flawed. For instance, mistakenly using multiplication instead of addition (5 * 2 instead of 5 + 2) results in incorrect output.

Python exceptions are triggered automatically by specific situations during execution. However, developers can also create user-defined exceptions to handle custom scenarios.

Categories of Errors

There are two main types of errors: syntax errors and exceptions. Syntax errors arise from not following programming language rules, causing the program to halt execution.

Exceptions are raised due to internal events that disrupt the normal flow of a program even if the code itself is correct.

Understanding Syntax Errors

Syntax errors occur when code does not adhere to programming language rules and are detected during parsing. They prevent any further execution until corrected.

When a syntax error occurs, the interpreter stops processing and requires rectification before rerunning the program.

Examples of Common Errors

An example includes defining a variable incorrectly or trying to print an undefined variable (e.g., printing y without defining it first).

Type errors can occur when combining incompatible data types (e.g., adding an integer with a string), leading to unexpected behavior or crashes.

Handling Division by Zero

Attempting division by zero raises a specific type of error known as "ZeroDivisionError," which halts execution until resolved.

Interactive vs Script Mode Errors

In interactive mode (shell mode), immediate feedback on errors like name or type errors is provided directly after inputting code.

In script mode, syntax errors may appear in dialog boxes with detailed descriptions about what went wrong, aiding debugging efforts.

This structured overview captures key concepts related to runtime errors and exceptions in Python programming based on the provided transcript.

Understanding Exceptions in Python

What is an Exception?

An exception occurs even if a statement or expression is written correctly; errors can still arise during program execution, such as failing to open a file or dividing by zero.

Handling Exceptions

When an error occurs, it stops the normal execution of the program. This interruption is referred to as an exception, which programmers need to handle properly.

If exceptions are not handled correctly, Python raises an issue that causes the program to halt unexpectedly.

Using Try and Except Blocks

Programmers use try and except blocks to manage exceptions and prevent programs from crashing.

Exception handling involves writing additional code within these blocks to provide proper messages and instructions when encountering errors.

Importance of Exception Handling

Every exception must be handled by the programmer to avoid sudden crashes of the program.

The process of generating messages and instructions during exceptions helps maintain program stability without abrupt interruptions.

Types of Exceptions

There are two main types of exceptions: built-in exceptions and user-defined exceptions. Built-in exceptions are predefined in Python's interpreter.

Built-in Exceptions

Built-in exceptions are common errors defined in the compiler/interpreter, allowing for standard error handling procedures in Python programs.

The Python standard library contains extensive collections of built-in exceptions that deal with common occurring errors effectively.

Common Built-in Exceptions

Syntax Error

A syntax error arises when there is an issue with the syntax rules in Python code, such as missing closing quotes on strings.

Value Error

A value error occurs when a built-in method receives an argument with the correct data type but inappropriate value, leading to mismatches.

I/O Error

An I/O error happens when a specified file cannot be opened due to various reasons like non-existence or incorrect path specifications.

Error Handling in Programming

Common Types of Errors

Import Error: Raised when a requested module is not found. This occurs if the module name is incorrect or does not exist.

EOF Error (End of File): Triggered when an attempt to read data from a file reaches the end without any data being available. The cursor has moved past the last character.

Zero Division Error: Occurs when there is an attempt to divide a number by zero, which is mathematically undefined.

Index Error: Raised when trying to access an index that is out of range in a sequence like lists or tuples. For example, accessing the seventh element in a list with only five elements.

Name Error: Happens when attempting to use a variable that has not been defined locally or globally, leading to confusion about its existence.

Additional Errors and Their Causes

Indentation Error: Arises due to incorrect indentation in code blocks, affecting control structures like loops and functions.

Type Error: Triggered when an operation receives an argument of an inappropriate type, such as adding an integer and a string together.

Overflow Error: Occurs when calculations exceed the maximum limit for numeric data types. For instance, trying to store 105 in a variable that can only hold up to 100.

User-defined Exceptions

User-defined Exceptions: Programmers can create custom exceptions based on specific conditions within their applications. This allows for tailored error handling suited to unique requirements.

Practical Example of Exception Handling

A practical demonstration involves using try-except blocks in code. If errors occur during execution (e.g., type mismatches), they can be caught and handled gracefully instead of crashing the program.

In this example, if variables are assigned values incorrectly (like changing from integer 7 to string 'seven'), it results in a TypeError which interrupts program flow unless properly managed through exception handling techniques.

Understanding Error Handling in Python

Introduction to Input and Variables

The speaker demonstrates how to input numbers into variables, using x for the first number and y for the second.

A simple addition operation is performed with these variables, showcasing that the code runs correctly without issues initially.

Error Generation and Handling

The speaker introduces a potential error by changing one of the inputs to an invalid value (e.g., "O" instead of 1), which causes a ValueError.

To manage this error, the speaker suggests using a try block to catch exceptions that may arise during execution.

Try and Except Blocks

It is emphasized that after writing a try block, an except block must be included to handle any errors that occur.

The speaker provides an example message ("Value Error") that will be displayed if an error occurs during execution.

Code Execution Flow

When running the code with valid inputs, it executes successfully; however, introducing an error shows how the program can fail gracefully with proper handling.

The importance of setting up clear messages in the except block is highlighted for better user understanding when errors occur.

Structure of Exception Handling

The four essential blocks in Python's exception handling are: try, except, else, and finally. Each serves a specific purpose in managing code execution flow.

If no exceptions are raised within the try block, the else clause can execute additional code; otherwise, control passes to except.

Final Thoughts on Exception Management

Effective exception handling ensures stable program performance by anticipating potential errors and providing alternative solutions or warnings.

The use of try-except statements allows developers to catch exceptions within their code effectively while maintaining overall functionality.

Practical Example of Exception Handling

An example illustrates how to write both try and except blocks where specific operations are attempted inside try while corresponding error management occurs in except.

By executing sample code involving variable assignments and arithmetic operations within these blocks, users can see firsthand how errors are managed seamlessly.

Error Handling in Programming

Understanding Error Sources

The discussion begins with identifying the source of an error that occurred due to data not being received for variable y. The speaker emphasizes the importance of ensuring values are correctly assigned before proceeding.

A specific example is provided where setting x to 10 and y to 3 allows the code to run without errors. This highlights how proper value assignment can prevent exceptions.

Exception Handling Techniques

The speaker explains that converting a number (like 3) into a string introduces a new error, indicating that understanding data types is crucial in programming.

It is suggested that multiple try-except blocks can be used within a single code segment to handle different types of exceptions effectively.

Specific Exceptions Explained

The concept of specific exceptions, such as "Zero Division Error," is introduced. This type of error occurs when attempting to divide by zero, which is an invalid operation in programming.

An example illustrates how to handle this exception by providing custom messages when errors occur, enhancing user experience and debugging processes.

Practical Application of Exception Handling

When running tests with various numbers, it’s shown that entering zero triggers a "Zero Division Error." This reinforces the need for robust error handling mechanisms in code.

The speaker discusses how built-in exceptions can provide informative messages about errors, which can be stored in variables for further processing or display.

Enhancing User Input Management

Emphasis is placed on printing out exception messages stored in variables like E, demonstrating how programmers can communicate issues back to users effectively.

If no action is taken within an except block (e.g., using 'pass'), the program will continue but may not provide useful feedback regarding what went wrong during execution.

Advanced Exception Scenarios

Additional examples show how multiple exception handlers can be implemented for different scenarios, allowing more granular control over error management based on varying conditions encountered during runtime.

The discussion includes potential situations where file handling might fail due to incorrect file names or paths, emphasizing the necessity for careful input validation and error handling strategies when dealing with external resources.

File Handling and Exception Management in Python

Understanding File Deletion and Error Handling

If a file is deleted, you can write its name in the try block to attempt opening it. If successful, it will read and print the string; otherwise, a "file not found" error will be stored in variable E.

An explanation follows if an error occurs while trying to load a file (e.g., sample.xt). The issue may arise from incorrect naming, preventing the file from being opened.

Multiple Exceptions Handling

A try statement can have multiple except clauses to specify handlers for different exceptions. For instance, handling both ZeroDivisionError and NameError by defining separate except blocks.

When encountering a NameError due to undefined variables (like 'name'), the code execution halts at that point unless handled properly.

Try with Else Block

The else block executes only if no exceptions are raised in the try block. This allows for additional statements to run when everything goes smoothly.

If an exception occurs within the try block, control moves directly to the except clause without executing any subsequent lines in the else block.

Finally Block Usage

The finally block runs regardless of whether an exception occurred or not. It is essential for cleaning up resources like closing files or releasing memory space.

Using finally ensures that critical cleanup actions are performed even if errors occur during program execution. It's common practice when working with file handling in Python.

This structured overview captures key concepts related to file handling and exception management as discussed in the transcript, providing clear insights into how these elements function within Python programming.

Understanding Exception Handling in Python

The Structure of Try-Except-Finally Blocks

The speaker emphasizes the importance of using the finally block at the end of a try-except structure, indicating that it should be placed after all other blocks to ensure proper execution.

An example is provided where the speaker demonstrates writing code within a finally block, highlighting its role in executing code regardless of whether an error occurs.

The discussion includes how errors can still arise even when using try-except structures, as shown by running code that results in a name error despite being wrapped in exception handling.

Importance of User Interaction and Feedback

The speaker encourages viewers to leave comments on their understanding and experiences with exception handling, noting that feedback motivates content creators to improve their material.

Viewers are urged to like videos as it helps gauge the effectiveness of the content delivered and indicates viewer engagement beyond mere views.

Generating Custom Exceptions

Transitioning into custom exceptions, the speaker explains how users can create specific scenarios (like overflow or underflow conditions) by generating exceptions based on user-defined criteria.

It is noted that every time an error is detected in a program, Python's interpreter raises an exception which can be handled accordingly.

Raising Exceptions Intentionally

Programmers have the ability to forcefully raise exceptions using raise and assert statements. This allows for more control over program flow based on specific conditions defined by developers.

The raise statement is explained as a tool for throwing exceptions when certain conditions are met, allowing programmers to interrupt normal execution based on requirements.

Practical Examples of Raising Exceptions

A practical example illustrates how raising an exception works: if age input is less than 16 or 18, appropriate messages will be displayed indicating invalid input or child labor concerns.

Further examples clarify how different inputs lead to different outcomes—either triggering an exception or proceeding with normal execution depending on user input values.

Understanding Error Handling in Programming

Exception Handling with Conditions

The discussion begins with a condition check where if the value exceeds five, an error message "Cannot execute" is triggered. This highlights how conditions can dictate program flow.

An IndexError can be raised when certain conditions are not met. The speaker emphasizes that custom messages can be passed along with exceptions to provide clarity on the error encountered.

The use of assert statements is introduced, which allows programmers to specify conditions that must hold true; if they do not, an exception is raised automatically.

Practical Examples of Assertions

A practical example illustrates using an assertion to check if a number (n) is greater than or equal to zero. If true, it proceeds normally; otherwise, it raises an error.

When calling the function with a negative number (-3), the assertion fails and generates a message indicating that the input does not meet the required condition.

Understanding Assertion Behavior

The assertion mechanism operates without needing explicit 'if else' statements. It inherently checks conditions and generates messages upon failure, simplifying error handling in code.

The session concludes by summarizing key points discussed about assertions and their role in managing errors effectively within programming contexts. Further topics will be explored in upcoming videos.