What types of exceptions are there in Python? Introduction to python exception handling

What this article brings to you is what types of exceptions are there in python? The introduction to Python exception handling has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Exception handling is a mechanism in a programming language or computer hardware that is used to handle abnormal conditions that occur in software or information systems (that is, certain special conditions that exceed the normal execution flow of the program).

1. Types of exceptions

There are many types of exceptions. Common exceptions include:

AttributeError 试图访问一个对象没有的属性，比如foo.x，但是foo没有属性x IOError 输入/输出异常；基本上是无法打开文件 ImportError 无法引入模块或包；基本上是路径问题或名称错误 IndentationError 语法错误（的子类） ；代码没有正确对齐 IndexError 下标索引超出序列边界，比如当x只有三个元素，却试图访问x[5] KeyError 试图访问字典里不存在的键 KeyboardInterrupt Ctrl+C被按下 NameError 尝试访问一个没有申明的变量 SyntaxError Python代码非法，代码不能编译(个人认为这是语法错误，写错了） TypeError 传入对象类型与要求的不符合 UnboundLocalError 试图访问一个还未被设置的局部变量，基本上是由于另有一个同名的全局变量，导致你以为正在访问它 ValueError 传入一个调用者不期望的值，即使值的类型是正确的

Other exceptions:

Exception can catch any exception

BaseException 所有异常的基类 SystemExit 解释器请求退出 KeyboardInterrupt 用户中断执行(通常是输入^C) Exception 常规错误的基类 StopIteration 迭代器没有更多的值 GeneratorExit 生成器(generator)发生异常来通知退出 StandardError 所有的内建标准异常的基类 ArithmeticError 所有数值计算错误的基类 FloatingPointError 浮点计算错误 OverflowError 数值运算超出最大限制 ZeropisionError 除(或取模)零 (所有数据类型) AssertionError 断言语句失败 AttributeError 对象没有这个属性 EOFError 没有内建输入,到达EOF 标记 EnvironmentError 操作系统错误的基类 IOError 输入/输出操作失败 OSError 操作系统错误 WindowsError 系统调用失败 ImportError 导入模块/对象失败 LookupError 无效数据查询的基类 IndexError 序列中没有此索引(index) KeyError 映射中没有这个键 MemoryError 内存溢出错误(对于Python 解释器不是致命的) NameError 未声明/初始化对象 (没有属性) UnboundLocalError 访问未初始化的本地变量 ReferenceError 弱引用(Weak reference)试图访问已经垃圾回收了的对象 RuntimeError 一般的运行时错误 NotImplementedError 尚未实现的方法 SyntaxError Python 语法错误 IndentationError 缩进错误 TabError Tab 和空格混用 SystemError 一般的解释器系统错误 TypeError 对类型无效的操作 ValueError 传入无效的参数 UnicodeError Unicode 相关的错误 UnicodeDecodeError Unicode 解码时的错误 UnicodeEncodeError Unicode 编码时错误 UnicodeTranslateError Unicode 转换时错误 Warning 警告的基类 DeprecationWarning 关于被弃用的特征的警告 FutureWarning 关于构造将来语义会有改变的警告 OverflowWarning 旧的关于自动提升为长整型(long)的警告 PendingDeprecationWarning 关于特性将会被废弃的警告 RuntimeWarning 可疑的运行时行为(runtime behavior)的警告 SyntaxWarning 可疑的语法的警告 UserWarning 用户代码生成的警告

##2. Catch exceptions and handle them Exception

#Exception handling can only be performed if the corresponding exception type is captured

Exception capture and processing method:

try: #程序执行的代码，异常检测的代码 pass except Exception as e: #捕获异常后进行的代码， print(e) pass else: #没有捕获到相应的异常后进行的代码 pass finally: #不论有没有异常捕获最后都要执行的代码 pass

The except here is like catch in java

You can also add multiple except statements in the code to catch different types of exceptions and execute different Operation

3. Actively throw an exception

Exception throwing can be added manually

try: raise Exception("我自己抛的") except Exception as e: print(e)#这里会输出“我自己抛的”

4. Custom exception type

We can define the type of exception we need

Mainly use the __str__ method in the class to achieve

class myException(BaseException): def __init__(self,message): self.message=message def __str__(self): return self.message try: raise myException('自定义的异常类型') except myException as e: print(e)　

5. Assertion

Assertion assert is used to determine whether a certain condition is true. If it is not true, an AssertionError exception is thrown. This exception can be captured

##

assert 条件 #相当于 if not 条件 : raise AssertionError() assert 条件,"描述" #相当于 if not 条件 : raise AssertionError("描述")

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