Python中的用户定义异常

待我称王封你为后i 2023-03-05 10:57 25阅读 0赞

Python has a lot of built-in exceptions like **ZeroDivisionError**, **IndexError**, **ImportError**, **TypeError**, etc but when built-in the exception is not enough to handle our requirements then we **create own customized exception**. Python allows us to create our exception from the base class exception. To understand it in a better way, let's take an example that raises the error if we will try to find the square root of a negative number. Suppose, we try to find the square root of the -9 then we will get the output in the form of the imaginary number as we all know but here we will write a Python program that raises an error instead of showing the imaginary number and we will handle it by using the **try-except statement**.

Python有很多内置的异常，例如**ZeroDivisionError** ， **IndexError** ， **ImportError** ， **TypeError**等，但是当内置的异常不足以满足我们的要求时，我们将**创建自己的自定义异常** 。 Python允许我们从基类异常中创建异常。 为了更好地理解它，让我们举一个如果发现负数的平方根会引发错误的示例。 假设我们尝试找到-9的平方根，然后我们将以虚数的形式获得输出，但是在这里，我们将编写一个引发错误而不是显示虚数的Python程序，我们将通过使用**try-except语句**来处理它。

Before going to write the Python program, we will the **syntax of the try-except statement**,

在编写Python程序之前，我们将**使用try-except语句**的**语法** ，

try:
           #statement or line of code
        except typeofError:
           #statement or line of code

Now, we will see the program in which we will **create the user-defined exception** to overcome the problem of imaginary number and again we handle it by using the try-except statement.

现在，我们将看到一个程序，其中将**创建用户定义的异常**来克服虚数的问题，然后再次使用try-except语句对其进行处理。

**Program:**

**程序：**

# creating child class from base class Exception
    class Error(Exception): 
        pass   # dummy function
    class InvalidNumberError(Error):
        def __init__(self,statement,s): # constructer
            self.statement=statement
            self.s=s
    number=int(input('Enter a Number: '))
    
    try:
        if number<1: # condition checking
            raise InvalidNumberError('You have entered a negative number.',number)
        else:
          print('The square root of the number:',(number)**0.5)
    except InvalidNumberError as e: #user defined exception handling
        print(e.statement)

**Output**

**输出量**

RUN 1:
    Enter a Number: 5
    The square root of the number: 2.23606797749979
    
    RUN 2:
    Enter a Number: -5
    You have entered a negative number.

> 翻译自: [https://www.includehelp.com/python/user-defined-exception.aspx][https_www.includehelp.com_python_user-defined-exception.aspx]

[https_www.includehelp.com_python_user-defined-exception.aspx]: https://www.includehelp.com/python/user-defined-exception.aspx