When to use exception Python?

Kenneth 82 Published: 12/07/2024

When to use exception Python?

I'm happy to respond in English for this question!

Exception handling is an essential concept in programming, and it's crucial to understand when to use exceptions in your code. In Python, exceptions are a mechanism to handle unexpected events or errors that occur during the execution of your program.

When to Use Exceptions:

Error Handling: One of the primary uses of exceptions is to handle runtime errors or exceptions that might occur during the execution of your code. For instance, if you're working with files and an I/O error occurs, you can use exceptions to catch the error, log it, and provide a meaningful message to the user.

Example:

try:

file = open("file.txt", "r")


except FileNotFoundError:


print("The file does not exist.")
Flow Control: Exceptions can be used as an alternative to traditional control structures like if-else statements or switch statements. You can raise exceptions to change the flow of your program, for instance, when you need to exit a loop or skip certain sections of code.

Example:

def validate_input():

while True:


try:


num = int(input("Enter a number: "))


if num < 0:


raise ValueError("Number must be non-negative.")


return num


except ValueError as e:


print(f"Invalid input: {e}")


num = validate_input()


print(f"The validated number is: {num}")
Decoupling: Exceptions can help decouple parts of your code that might not be related otherwise. For instance, you can raise an exception from a service layer to notify the presentation layer about an error.

Example:

class ServiceLayer:

def do_something(self):


try:

some code

except Exception as e:


raise CustomException("Error occurred in service layer.")


try:


service = ServiceLayer()


service.do_something()


except CustomException as e:


print(f"Caught exception: {e}")
Logging and Debugging: Exceptions can be used to log errors or provide debug information about your program's execution.

Example:

import logging

try:

some code

except Exception as e:


logging.error(f"Error occurred: {e}")


logging.info("Debug message")

In summary, exceptions are a powerful mechanism in Python that helps you handle unexpected events or errors. You can use them to handle runtime errors, control the flow of your program, decouple parts of your code, and log or debug issues.

Remember, exceptions should be used judiciously, as overusing them can make your code harder to understand and maintain.

When to use nonlocal python w3schools

I'd be happy to help you with that.

What is Non-Local in Python?

In Python, a non-local function is a function that has access to the scope and variables of a higher-level (outer) scope, even when it's called from within a lower-level (inner) scope. This means that a non-local function can modify or read variables from a different scope than its own.

Why Use Non-Local?

Using non-local functions can be very useful in certain situations:

Modifying Outer Scope Variables: Imagine you have a nested loop, and you want to modify a variable defined in the outer scope. You can create a non-local function that has access to this variable. Accessing Outer Scope Functions: Sometimes, you might need to call a function defined in an outer scope from within an inner scope. A non-local function can help you do this. Simplifying Code: Non-local functions can simplify your code by reducing the number of nested loops or variables.

W3Schools: How to Use Non-Local Functions in Python

According to W3Schools, to use a non-local function in Python:

Create a Non-Local Function: Define a function that has access to the outer scope's variables. Pass the Outer Scope as an Argument: Pass the outer scope (or self) as an argument to your non-local function.

Here is an example of how you might use a non-local function:

def outer_function():

x = 10


def inner_function(y):


nonlocal x


x += y


return x


return inner_function


f = outer_function()


print(f(5))  # Output: 15

In this example, the inner_function has access to the variable x from the outer_function, even though it's called from within the inner_function. This is because inner_function has been passed the scope of outer_function as an argument.

Conclusion

Non-local functions in Python are a powerful tool that can simplify your code and help you achieve complex tasks. By understanding how to use non-local functions, you'll be able to write more concise and efficient code.

So, go ahead and explore the world of non-local functions with W3Schools!

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