Python Day-例外处理

>示例：

>
• 1）

• try:
      no1 = int(input("enter no."))
      no2 = int(input("enter no. "))
      print(no1//no2)
  except zerodivisionerror:
      print("no2 should not be zero. check no2 value ")
  print(no1+no2)
  

>输出：

enter no.10
enter no. 0
no2 should not be zero. check no2 value 
10

try:
    no1 = int(input("enter no."))
    no2 = int(input("enter no. "))
    print(no1//no2)
    print(no1+no2)
except zerodivisionerror:
    print("no2 should not be zero. check no2 value ")
except valueerror:
    print("inputs should be numbers ")

>输出：

enter no.10
enter no. ten
inputs should be numbers

3）

try:
    no1 = int(input("enter no."))
    no2 = int(input("enter no. "))
    print(no1//no2)
    print(no1+no2)
    f = open("pqrs.txt")
except zerodivisionerror:
    print("no2 should not be zero. check no2 value ")
except valueerror:
    print("inputs should be numbers ")
except:
    print("something went wrong")

>输出：

#if all inputs are correct
enter no.10
enter no. 5
2
15

#if any error not specified particularly
enter no.10
enter no. 5
2
15
something went wrong

#if zerodivisionerror
enter no.10
enter no. 0
no2 should not be zero. check no2 value

#if valueerror
enter no.10
enter no. ten
inputs should be numbers 

：

**注意：**
- 处理不可预测的错误时，请使用try-exce ->处理预期条件时使用if-else

追溯模块：

>示例：1

import traceback
try:
    no1 = int(input("enter no."))
    no2 = int(input("enter no. "))
    print(no1//no2)
    print(no1+no2)
    f = open("pqrs.txt")
    print(f.read())
except (valueerror, zerodivisionerror) as msg:
    print("check ",msg)

except:
    print("something went wrong")
    traceback.print_exc()

>输出：

enter no.10
enter no. 0
check  integer division or modulo by zero

import traceback
try:
    no1 = int(input("enter no."))
    no2 = int(input("enter no. "))
    print(no1//no2)
    print(no1+no2)
    f = open("pqrs.txt")
    print(f.read())
except (valueerror, zerodivisionerror) as msg:
    print("check ",msg)
except:
    print("something went wrong")
    traceback.print_exc()
finally:
    print("check finally message")

>输出：

enter no.10
enter no. 10
1
20
something went wrong
traceback (most recent call last):
  file "/home/guru/desktop/guru/python/user.py", line 7, in 
    f = open("pqrs.txt")
        ^^^^^^^^^^^^^^^^
filenotfounderror: [errno 2] no such file or directory: 'pqrs.txt'
check finally message

捕获多个特定异常：

> ->我们可以在单个单个中处理多个异常，除了使用元组。
->使用，因为我们也可以为异常提供一个可变名称。

trackback.print_exc（）：它提供详细的错误信息（行号，错误类型，消息）。

class employee:
    pass

emp1 = employee()
emp2 = employee()
print(emp1)
print(emp2)

<__main__.employee object at 0x730a36434110>
<__main__.employee object at 0x730a36434080>

pass关键字的意思是“无所事事”（占位符），因此该类目前为空（它没有属性或方法）。

__ doc __（docstring属性）

> __doc__属性用于访问类，功能，模块或方法的docstring。 docstring是一个多行字符串，提供有关对象的文档，该对象在triple引号（''''''）中声明。 >示例：

class employee:
    '''this class is for creating employees'''
print(employee.__doc__)

4

this class is for creating employees

自我关键字：

->“ self”用于访问和操纵类中的实例变量和方法。 -> self代表类的实例。>

>特定对象的

- 使用self.variable_name定义的>。 ->对于每个对象唯一。

>示例：1

class employee:
    def work(self):
        print(self.empname, self.job_nature)

emp1 = employee()
emp1.empname = 'guru'
emp1.job_nature = "designing"
emp2 = employee()
emp2.empname = "pritha"
emp2.job_nature = "development"
emp1.work()
emp2.work()

>输出：

guru designing
pritha development

class employee:
    organization = "infosys"
    def work(self):
        print(self.empname, self.job_nature, self.organization)
    def take_leave(self):
        pass
    def promote(self):
        pass

emp1 = employee()
emp1.empname = 'guru'
emp1.job_nature = "designing"
emp2 = employee()
emp2.empname = "pritha"
emp2.job_nature = "development"
emp1.work()
emp2.work()

>输出：

guru designing infosys
pritha development infosys

类特定信息：
类别的信息是指在类的所有实例（对象）之间共享的数据。

>示例：

class employee:
    def work(self):
        print(self.empname, self.job_nature, self.organization)

    def take_leave(self):
        pass

    def promote(self):
        pass

emp1 = employee()
emp1.empname = 'guru'
emp1.job_nature = "designing"
emp2 = employee()
emp2.empname = "pritha"
emp2.job_nature = "development"
employee.organization = "infosys"
emp1.work()
emp2.work()

>输出：

Guru designing Infosys
Pritha development Infosys

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