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Errors & debugging

Handle failures gracefully, raise helpful errors, and debug with confidence.

7 matches

How to Catch ValueError in Python (try except)

Handle invalid numeric input by catching ValueError in a try/except block and returning a friendly error message.

def parse_number(text):
    try:
        number = int(text)
        return f"Parsed number: {number}"
    except ValueError as error:
        return f"Error: '{text}' is not a valid number ({error})"


if __name__ == "__main__":
    examples = ["42", "hello", "3.14", "100"]
    for item in examples:
        print(pars…

11 0 Open

Errors & debugging easy

How to Record Last N Errors with a Ring Buffer in Python

Use collections.deque with maxlen to keep only the most recent N error messages while discarding older entries automatically.

ring-buffer deque error-handling

Python

import collections

class ErrorRecorder:
    def __init__(self, size):
        self.buffer = collections.deque(maxlen=size)

    def record_error(self, message):
        self.buffer.append(message)

    def get_errors(self):
        return list(self.buffer)

if __name__ == "__main__":
    recorder = ErrorRecorder(3)
 …

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Errors & debugging easy

How to Validate an Email Address and Raise ValueError in Python

This code defines a validate_email function that checks an email address against a regex pattern and several rules, raising ValueError with a specific reason when invalid.

validation regex errors

Python

import re

def validate_email(email: str) -> str:
    """Validate an email address and return it if valid, otherwise raise ValueError."""
    if not isinstance(email, str):
        raise ValueError("Email must be a string")
    if len(email) > 254:
        raise ValueError("Email length exceeds 254 characters")

    #…

14 0 Open

Errors & debugging easy

How to check for None and raise helpful errors in Python

A defensive function that explicitly validates data, keys, and values — raising descriptive ValueError and KeyError exceptions before returning a result.

none error-handling validation

Python

def get_value(data, key):
    if data is None:
        raise ValueError("data cannot be None")
    if key not in data:
        raise KeyError(f"key '{key}' not found in data")
    result = data[key]
    if result is None:
        raise ValueError(f"value for key '{key}' is None")
    return result


if __name__ == "__…

15 0 Open

Errors & debugging easy

How to define an exception hierarchy for domain errors in Python

Create a custom exception hierarchy with a base DomainError class and specific subclasses to handle validation, not-found, permission, and concurrency errors cleanly in Python apps.

exceptions domain-errors error-handling

Python

class DomainError(Exception):
    """Base class for all domain errors."""
    pass

class ValidationError(DomainError):
    """Raised when input data fails validation rules."""
    pass

class NotFoundError(DomainError):
    """Raised when a requested entity does not exist."""
    pass

class PermissionDeniedError(Dom…

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Errors & debugging easy

Try Except ValueError in Python: Handle Conversion Errors

Catch ValueError exceptions when converting strings to integers or performing arithmetic, returning None on failure instead of crashing.

try-except valueerror exception

Python

def convert_to_int(value):
    try:
        return int(value)
    except ValueError as error:
        print(f"Conversion failed: {error}")
        print(f"Problem value was: {repr(value)}")
        return None


def divide_numbers(numerator, denominator):
    try:
        result = numerator / denominator
        retur…

13 0 Open

Errors & debugging easy

Validate try except ValueError handler for beginners — errors debugging

Learn how to validate user input and handle division errors safely using try/except with ValueError and ZeroDivisionError in Python.

try except valueerror

Python

def divide_numbers(a, b):
    """Divide two numbers, catching division by zero and value errors."""
    try:
        result = a / b
    except ZeroDivisionError:
        print("Error: Cannot divide by zero!")
        return None
    except TypeError:
        print("Error: Both arguments must be numbers!")
        retu…

14 0 Open

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