242 lines
6.2 KiB
Python
242 lines
6.2 KiB
Python
"""
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调试流程示例
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这个示例展示了完整的调试流程，从发现问题到解决问题。
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"""
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import logging
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# 配置日志
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logging.basicConfig(level=logging.DEBUG, format='%(asctime)s - %(levelname)s - %(message)s')
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logger = logging.getLogger(__name__)
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# ============================================
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# 问题 1：IndexError
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# ============================================
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def get_item(items, index):
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"""
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问题：直接访问索引可能导致 IndexError
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错误现象：
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IndexError: list index out of range
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"""
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# ❌ 有问题的代码
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# return items[index]
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# ✅ 修复后的代码
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if 0 <= index < len(items):
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return items[index]
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else:
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logger.warning(f"索引 {index} 超出范围 [0, {len(items)})")
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return None
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# ============================================
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# 问题 2：TypeError - 字符串拼接
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# ============================================
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def format_message(name, count):
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"""
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问题：尝试拼接字符串和数字
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错误现象：
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TypeError: can only concatenate str (not "int") to str
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"""
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# ❌ 有问题的代码
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# return name + ": " + count
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# ✅ 修复后的代码
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return f"{name}: {count}"
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# 或
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# return name + ": " + str(count)
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# ============================================
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# 问题 3：KeyError
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# ============================================
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def get_user_info(users, user_id):
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"""
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问题：直接访问字典中可能不存在的键
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错误现象：
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KeyError: 'user_123'
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"""
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# ❌ 有问题的代码
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# return users[user_id]
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# ✅ 修复后的代码 - 方法1：使用 get()
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return users.get(user_id, None)
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# ✅ 修复后的代码 - 方法2：检查键是否存在
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# if user_id in users:
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# return users[user_id]
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# return None
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# ============================================
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# 问题 4：AttributeError - None 对象
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# ============================================
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def process_data(data_provider):
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"""
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问题：data_provider 可能返回 None
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错误现象：
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AttributeError: 'NoneType' object has no attribute 'process'
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"""
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data = data_provider.get_data()
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# ❌ 有问题的代码
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# return data.process()
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# ✅ 修复后的代码
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if data is not None:
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return data.process()
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else:
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logger.error("数据为 None，无法处理")
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return None
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# ============================================
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# 问题 5：修改正在迭代的列表
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# ============================================
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def remove_even_numbers(numbers):
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"""
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问题：迭代时修改列表导致跳过元素
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错误现象：
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某些偶数没有被移除
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"""
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# ❌ 有问题的代码
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# for num in numbers:
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# if num % 2 == 0:
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# numbers.remove(num)
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# return numbers
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# ✅ 修复后的代码 - 方法1：列表推导式
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return [num for num in numbers if num % 2 != 0]
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# ✅ 修复后的代码 - 方法2：使用副本
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# for num in numbers[:]:
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# if num % 2 == 0:
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# numbers.remove(num)
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# return numbers
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# ============================================
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# 调试技巧示例
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# ============================================
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def debug_with_logging(data):
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"""
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使用日志追踪问题
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"""
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logger.debug(f"输入数据: {data}")
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# 步骤 1
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processed = step1(data)
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logger.debug(f"步骤1结果: {processed}")
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# 步骤 2
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result = step2(processed)
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logger.debug(f"步骤2结果: {result}")
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return result
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def step1(data):
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"""模拟步骤1"""
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return [x * 2 for x in data]
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def step2(data):
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"""模拟步骤2"""
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return sum(data)
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# ============================================
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# 异常处理示例
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# ============================================
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def safe_divide(a, b):
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"""
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正确的异常处理模式
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"""
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try:
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result = a / b
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logger.info(f"{a} / {b} = {result}")
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return result
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except ZeroDivisionError:
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logger.error(f"除数不能为零: {b}")
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return None
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except TypeError as e:
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logger.error(f"类型错误: {e}")
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return None
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# ============================================
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# 使用断言进行调试
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# ============================================
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def calculate_discount(price, discount_rate):
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"""
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使用断言验证假设
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"""
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# 断言：价格应该是正数
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assert price > 0, f"价格应该是正数，实际: {price}"
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# 断言：折扣率应该在 0-1 之间
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assert 0 <= discount_rate <= 1, f"折扣率应该在 0-1 之间，实际: {discount_rate}"
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discounted_price = price * (1 - discount_rate)
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# 断言：折扣后的价格应该小于原价
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assert discounted_price <= price, "折扣价格应该小于原价"
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return discounted_price
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# ============================================
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# 测试代码
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# ============================================
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if __name__ == "__main__":
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print("=" * 50)
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print("调试示例")
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print("=" * 50)
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# 测试 get_item
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print("\n1. 测试 get_item:")
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items = ['a', 'b', 'c']
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print(f"get_item(items, 1) = {get_item(items, 1)}")
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print(f"get_item(items, 10) = {get_item(items, 10)}")
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# 测试 format_message
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print("\n2. 测试 format_message:")
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print(f"format_message('Count', 42) = {format_message('Count', 42)}")
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# 测试 get_user_info
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print("\n3. 测试 get_user_info:")
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users = {'user_1': 'Alice', 'user_2': 'Bob'}
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print(f"get_user_info(users, 'user_1') = {get_user_info(users, 'user_1')}")
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print(f"get_user_info(users, 'user_999') = {get_user_info(users, 'user_999')}")
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# 测试 remove_even_numbers
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print("\n4. 测试 remove_even_numbers:")
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numbers = [1, 2, 3, 4, 5, 6]
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print(f"原始: {numbers}")
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print(f"结果: {remove_even_numbers(numbers)}")
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# 测试 safe_divide
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print("\n5. 测试 safe_divide:")
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print(f"safe_divide(10, 2) = {safe_divide(10, 2)}")
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print(f"safe_divide(10, 0) = {safe_divide(10, 0)}")
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# 测试 calculate_discount
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print("\n6. 测试 calculate_discount:")
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print(f"calculate_discount(100, 0.2) = {calculate_discount(100, 0.2)}")
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