How to handle boundary cases of input data — negative numbers, too large sums, incorrect values?

Handling edge cases of input data is an important aspect of reliable code. Here are approaches for different types of problems:

• Negative numbers: validate input data and throw exceptions or correct the value if necessary.
• Too large sums: use data types with a larger range (e.g., decimal or int64), check for overflow, and apply checks before calculations.
• Incorrect values: validate input data, for example, using regular expressions, type checks, or special libraries.

Example in Python:

def process_amount(amount):
    if not isinstance(amount, (int, float)):
        raise ValueError("Invalid data type")
    if amount < 0:
        raise ValueError("Amount cannot be negative")
    if amount > 1e9:
        raise ValueError("Amount is too large")
    # further processing
    return amount * 0.9

This approach helps to avoid errors and make the code more robust.