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Errors & debugging

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

6 matches

How to Catch KeyError with a Default Value in Python Dictionaries

Safely retrieve dictionary values while catching KeyError and handling None values by returning a default.

def get_value(data, key, default=None):
    """
    Safely get a value from a dictionary, returning a default if the key
    is missing or the value is None.
    """
    try:
        value = data[key]
        return value if value is not None else default
    except KeyError:
        return default


if __name__ == "_…

14 0 Open

Errors & debugging easy

How to Handle ValueError with try except in Python

Shows a beginner-friendly try/except pattern that catches ValueError when converting text to an integer, prints a helpful message, and returns None instead of crashing.

try-except valueerror error-handling

Python

def parse_number(text):
    try:
        return int(text)
    except ValueError:
        print(f"ValueError: '{text}' is not a valid integer.")
        return None


if __name__ == "__main__":
    user_input = "abc"
    result = parse_number(user_input)
    print(f"Parsing '{user_input}' returned: {result}")

    vali…

14 0 Open

Errors & debugging easy

How to Use Optional Return in Python Instead of Raising Exceptions

A Python function returns None for missing dictionary keys instead of raising KeyError, enabling graceful lookup handling with type hints.

optional typing dict-get

Python

from typing import Optional


def find_user(users: dict, user_id: int) -> Optional[dict]:
    """
    Look up a user by ID. Returns the user dict if found,
    otherwise returns None instead of raising KeyError.
    """
    return users.get(user_id)


def main() -> None:
    users = {
        1: {"name": "Alice", "ema…

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 handle ZeroDivisionError in Python

Wrap a division operation in try/except to return None or a friendly message instead of crashing when dividing by zero.

zero-division exception-handling try-except

Python

def safe_divide(a, b):
    """Return a/b if possible, else None when dividing by zero."""
    try:
        return a / b
    except ZeroDivisionError:
        return None


def safe_divide_with_message(a, b):
    """Return a how-to message on divide-by-zero error."""
    try:
        return a / b
    except ZeroDivisio…

13 0 Open

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

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