try-except statement
try:
Code is detected
except Exception [as reason]:
After an exception handling code
Example:
>>>try:
sum = 1+'1'
f = open ( 'undefined file .txt')
print(f.read())
f.close
except OSError as reason:
print ( 'file error it wrong reasons:!' + str (reason))
except TypeError as reason:
print ( 'type error' + str (reason))
Run Results: Type Error unsupported operand type (s) for +: 'int' and 'str'
Wherein the third row to the seventh row code is not running, because once the abnormal try statement, it will directly positioned to the corresponding sentence except to the rest of the detection code will not be executed
try-finally statement
try:
Code is detected
except Exception [as reason]:
After an exception handling code
finally:
Anyway the code to be executed
Example:
try:
f=open('123.txt','w')
print(f.write('hello'))
sum = 1 + '1' # exception occurs here skip f.close () statements, resulting in data writing can not be stored
f.close()
except (OSError,TypeError):
print ( 'it wrong!')
So you can use try-finally statement to avoid this situation, change:
try:
f=open('123.txt','w')
print(f.write('hello'))
sum = 1 + '1' # exception occurs here skip f.close () statements, resulting in data writing can not be stored
f.close()
except (OSError,TypeError):
print ( 'it wrong!')
finally:
f.close()
raise statement
Itself an exception is thrown
>>>try:
for each in range(3):
if each==1:
raise KeyboardInterrupt
print(each)
except KeyboardInterrupt:
print ( 'Quit it!')
0
Quit it
python standard exceptions summary
| AssertionError |
Assertion (assert) failure |
| AttributeError |
尝试访问未知的对象属性 |
| EOFError |
用户输入文件末尾标志EOF（Ctrl+d） |
| FloatingPointError |
浮点计算错误 |
| GeneratorExit |
generator.close()方法被调用的时候 |
| ImportError |
导入模块失败的时候 |
| IndexError |
索引超出序列的范围 |
| KeyError |
字典中查找一个不存在的关键字 |
| KeyboardInterrupt |
用户输入中断键（Ctrl+c） |
| MemoryError |
内存溢出（可通过删除对象释放内存） |
| NameError |
尝试访问一个不存在的变量 |
| NotImplementedError |
尚未实现的方法 |
| OSError |
操作系统产生的异常（例如打开一个不存在的文件） |
| OverflowError |
数值运算超出最大限制 |
| ReferenceError |
弱引用（weak reference）试图访问一个已经被垃圾回收机制回收了的对象 |
| RuntimeError |
一般的运行时错误 |
| StopIteration |
迭代器没有更多的值 |
| SyntaxError |
Python的语法错误 |
| IndentationError |
缩进错误 |
| TabError |
Tab和空格混合使用 |
| SystemError |
Python编译器系统错误 |
| SystemExit |
Python编译器进程被关闭 |
| TypeError |
不同类型间的无效操作 |
| UnboundLocalError |
访问一个未初始化的本地变量（NameError的子类） |
| UnicodeError |
Unicode相关的错误（ValueError的子类） |
| UnicodeEncodeError |
Unicode编码时的错误（UnicodeError的子类） |
| UnicodeDecodeError |
Unicode解码时的错误（UnicodeError的子类） |
| UnicodeTranslateError |
Unicode转换时的错误（UnicodeError的子类） |
| ValueError |
传入无效的参数 |
| ZeroDivisionError |
除数为零 |