Python异常对象Exception基础类异常捕捉

目录

• 异常对象
• 异常捕捉

异常对象

Python中遇到错误后，会引发异常。

Python中使用异常对象来表示异常情况。

如果异常对象未被处理或者捕捉，程序就会用所谓的回溯（traceback）来终止执行。

下面是一个例子：

def func1():
    raise Exception
if __name__ == "__main__":
    func1()

执行之后报错：

(venv) E:\Codes\python_everything\begining-python\src\08>list8-2.py
Traceback (most recent call last):
  File "E:\Codes\python_everything\begining-python\src\08\list8-2.py", line 19, in <module>
    func1()
  File "E:\Codes\python_everything\begining-python\src\08\list8-2.py", line 15, in func1
    raise Exception
Exception

异常有不同的类型，Exception是基础类，下面还有各种子类：

 +-- Exception
      +-- StopIteration
      +-- StandardError
      |    +-- BufferError
      |    +-- ArithmeticError
      |    |    +-- FloatingPointError
      |    |    +-- OverflowError
      |    |    +-- ZeroDivisionError
      |    +-- AssertionError
      |    +-- AttributeError
      |    +-- EnvironmentError
      |    |    +-- IOError
      |    |    +-- OSError
      |    |         +-- WindowsError (Windows)
      |    |         +-- VMSError (VMS)
      |    +-- EOFError
      |    +-- ImportError
      |    +-- LookupError
      |    |    +-- IndexError
      |    |    +-- KeyError
      |    +-- MemoryError
      |    +-- NameError
      |    |    +-- UnboundLocalError
      |    +-- ReferenceError
      |    +-- RuntimeError
      |    |    +-- NotImplementedError
      |    +-- SyntaxError
      |    |    +-- IndentationError
      |    |         +-- TabError
      |    +-- SystemError
      |    +-- TypeError
      |    +-- ValueError
      |         +-- UnicodeError
      |              +-- UnicodeDecodeError
      |              +-- UnicodeEncodeError
      |              +-- UnicodeTranslateError

还可以通过继承Exception来实现自己的类：

class SomeError(Exception): pass
def func2():
    raise SomeError
if __name__ == "__main__":
    func2()

异常捕捉

异常可以被捕捉，需要使用try...except...语句：

class SomeError(Exception): pass
def func2():
    raise SomeError
if __name__ == "__main__":
    try:
        func2()
    except SomeError:
        print("Some error happened")

这里捕捉到了参数，所以就不会回溯：

(venv) E:\Codes\python_everything\begining-python\src\08>list8-3.py
Some error happened

但是如果是其它的异常：

def func1():
    raise Exception
class SomeError(Exception): pass
def func2():
    raise SomeError
if __name__ == "__main__":
    try:
        func1()
    except SomeError:
        print("Some error happened")

这里的Exception就没有被捕获，所以还是会回溯：

(venv) E:\Codes\python_everything\begining-python\src\08>list8-3.py
Traceback (most recent call last):
  File "E:\Codes\python_everything\begining-python\src\08\list8-3.py", line 27, in <module>
    func1()
  File "E:\Codes\python_everything\begining-python\src\08\list8-3.py", line 15, in func1
    raise Exception
Exception

如果没有出现异常，则会继续往下执行，但是这里可以有else语句来执行没有异常时可以执行的语句，使整个逻辑更通顺：

if __name__ == "__main__":
    try:
        print("No exception")
    except SomeError:
        print("Some error happened")
    else:
        print("No error happened")

结果如下：

(venv) E:\Codes\python_everything\begining-python\src\08>list8-3.py
No exception
No error happened

但是有时即使发生了无法捕捉的异常，也想要执行一些语句，这个时候就可以使用finally语句：

def func1():
    raise Exception
class SomeError(Exception): pass
def func2():
    raise SomeError
if __name__ == "__main__":
    try:
        func1()
    except SomeError:
        print("Some error happened")
    else:
        print("No error happened")
    finally:
        print("Do something")

Python中更倾向于使用try...except...这样的语句来代替if...else..语句。

以上就是Python异常对象异常捕捉及Exception基础类的详细内容，更多关于Python对象Exception类异常捕捉的资料请关注我们其它相关文章！