python中的错误处理及异常断言详解

def divide(a, b):
    return a / b
result = divide(4, 0)  # ZeroDivisionError: division by zero

def safe_divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        print("Cannot divide by zero!")
        return None
result = safe_divide(4, 0)  # Cannot divide by zero!
print(result)  # None

def safe_divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        print("Cannot divide by zero!")
        return None
    except TypeError:
        print("Invalid input!")
        return None
result = safe_divide(4, "two")  # Invalid input!
print(result)  # None

def safe_divide(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        print("Cannot divide by zero!")
        return None
    except TypeError:
        print("Invalid input!")
        return None
    finally:
        print("Finished dividing.")
result = safe_divide(4, 2)  # Finished dividing.
print(result)  # 2.0
result = safe_divide(4, 0)  # Cannot divide by zero!
                             # Finished dividing.
print(result)  # None

class InvalidInputError(Exception):
    pass
def safe_divide(a, b):
    if not isinstance(a, (int, float)) or not isinstance(b, (int, float)):
        raise InvalidInputError("Both a and b must be numbers.")
    if b == 0:
        raise ZeroDivisionError("Cannot divide by zero.")
    return a / b
try:
    result = safe_divide(4, "two")
except InvalidInputError as e:
    print(e)  # Both a and b must be numbers.

```python
class ParsingError(Exception):
    pass
def parse_number(number_string):
    try:
        return int(number_string)
    except ValueError as e:
        raise ParsingError("Invalid number format.") from e
try:
    result = parse_number("12a")
except ParsingError as e:
    print(f"{e} - Original exception: {e.__cause__}")

def calculate_area(width, height):
    assert width > 0, "Width must be positive."
    assert height > 0, "Height must be positive."
    return width * height
try:
    area = calculate_area(-1, 5)
except AssertionError as e:
    print(e)  # Width must be positive.