Comprehensive Guide to Python Exception Handling

01 Basic Exception Throw and Catch

try:
    # Attempt code that may raise an exception
    result = 10 / 0
except ZeroDivisionError:
    # Code executed when ZeroDivisionError is caught
    print("除数不能为0")

02 Multiple Exception Captures

try:
    x = int(input("请输入一个数字: "))
    y = int(input("请输入另一个数字: "))
    result = x / y
except ValueError:
    print("输入的不是有效的数字")
except ZeroDivisionError:
    print("除数不能为0")

03 Using else and finally

try:
    f = open("myfile.txt")
    # File operations...
except FileNotFoundError:
    print("文件未找到")
else:  # Executed if no exception occurs
    print("文件处理完成")
finally:  # Executed regardless of exception
    f.close()

04 Custom Exceptions

class MyException(Exception):
    pass

def some_function():
    raise MyException("这是一个自定义异常")

try:
    some_function()
except MyException as e:
    print(e)

05 Exception Propagation: Throw Inside Function, Catch Outside

def divide(x, y):
    if y == 0:
        raise ZeroDivisionError("除数不能为0")
    return x / y

try:
    result = divide(10, 0)
except ZeroDivisionError as e:
    print(e)

06 Using raise ... from ... to Specify Exception Cause

def outer():
    try:
        inner()
    except Exception as e:
        raise ValueError("外层错误") from e

def inner():
    raise KeyError("内层错误")

try:
    outer()
except ValueError as e:
    print(e)  # Prints exception chain information

07 Exceptions in Context Managers

with open("nonexistent_file.txt") as f:
    content = f.read()
    # If the file does not exist, IOError is automatically caught and the file is closed

08 Using assert for Condition Checks

def apply_discount(product, discount):
    price = int(product['price'] * (1.0 - discount))
    assert 0 <= price <= product['price'], "无效的折扣"
    return price

product = {'name': 'Widget', 'price': 100}
try:
    print(apply_discount(product, 1.5))  # Discount > 1 triggers assert
except AssertionError as e:
    print(e)

09 Exception Suppression (Not Recommended)

try:
    # Code that may raise an exception
    ...
except:
    pass  # Silently ignore all exceptions (discouraged)

10 Selectively Ignoring Specific Exceptions with contextlib.suppress

from contextlib import suppress

with suppress(FileNotFoundError):
    with open("missing_file.txt") as f:
        read_data(f)
    # No exception is raised if the file does not exist