How to use Python's raise keyword?

General Discussions
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#1

How to use the python raise keyword? I have read the official definition of “raise”, but I still don’t quite understand what it does.

In simplest terms, what does python raise do?

Example usage would help.How to use the python raise keyword? I have read the official definition of “raise”, but I still don’t quite understand what it does.

In simplest terms, what does python raise do?

Example usage would help.

#2

Let’s start with the basics of the python raise keyword: It’s used to intentionally trigger exceptions. Think of it as a way to signal, ‘Something is wrong here!’ to your program. You can use raise to stop the program’s flow when you encounter an error, ensuring the issue is addressed immediately. Example:

def check_value(x):
    if x < 0:
        raise ValueError("Value must be non-negative")
    return x

check_value(-5)  # This raises a ValueError

In this case, if x is negative, we raise a ValueError with a helpful error message. Simple, right?

#3

Building on that, python raise becomes even more powerful when you want to proactively manage potential errors. By raising specific exceptions, you can make your code more robust and easier to debug. This means your program can preemptively catch mistakes before they cause deeper issues. Example:

try:
    x = int(input("Enter a number: "))
    if x < 0:
        raise ValueError("Input cannot be negative")
except ValueError as e:
    print(e)

Here, python raise helps us flag invalid user input. Notice how the exception is caught with a try...except block, letting us gracefully handle the error.

#4

That’s great for raising specific exceptions, but did you know you can also re-raise exceptions with python raise? This is super useful when you catch an exception but need to pass it along for someone else to handle—like throwing it back up the call stack while still adding your custom logic.

Example:
try:
    # Some code that might fail
    1 / 0
except ZeroDivisionError as e:
    print("Caught ZeroDivisionError, but it needs further handling.")
    raise  # Re-raises the same exception

Here, after catching the ZeroDivisionError, we use raise without specifying the exception to re-raise the original error. It’s like saying, ‘I’ve noted the issue, now someone else can deal with it!’ This technique keeps your error-handling structured and modular."

This way, each response flows naturally, progressively introducing more advanced concepts of the python raise keyword