100_异常

常见内置异常 - python 官方文档

try- 语句陈述 - 官网文档 - 复合语句

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异常处理

一些 示例

可以跟着敲一敲

# try + finally 
# it's work
In [1]: try:
   ...:     print("onepis")
   ...: finally:
   ...:     print("end")
   ...:
onepis
end

# try + except + finally 
# it's work
# 报错的时候  执行 except 里面的语句
# finally  不管是否报错 都执行
In [2]: try:
   ...:     raise ValueError("the value is error ")
   ...: except Exception as e:
   ...:     print("error")
   ...: finally:
   ...:     print("end")
   ...:
error
end

# try + except + finally 
# it's work

In [3]: try:
   ...:     raise ValueError("the value is error ")
   ...: except Exception as e:
   ...:     print(e)
   ...: finally:
   ...:     print("end")
   ...:
the value is error
end
# try + except + else +finally 
# it's work
# 报错的时候 else 里面的语句 不执行

In [4]: try:
   ...:     raise ValueError("the value is error ")
   ...: except Exception as e:
   ...:     print(e)
   ...: else:
   ...:     print("else")
   ...: finally:
   ...:     print("end")
   ...:
the value is error
end
# try + except +else + finally 
# it's work
# 没有报错
# 那么else 里面的语句执行
# 则 except 里面的语句 不执行
In [5]: try:
   ...:     #raise ValueError("the value is error ")
   ...:     print("it's ok")
   ...:
   ...: except Exception as e:
   ...:     print(e)
   ...: else:
   ...:     print("else")
   ...: finally:
   ...:     print("end")
   ...:
it's ok
else
end

# try + else + finally 
# 报错  语法错误
In [6]: try:
   ...:     #raise ValueError("the value is error ")
   ...:     print("it's ok")
   ...: else:
   ...:     print("else")
   ...: finally:
   ...:     print("end")
   ...:
  File "<ipython-input-6-03ea4e78e36a>", line 4
    else:
       ^
SyntaxError: invalid syntax

# try + else 
# 报错  语法错误
In [7]: try:
   ...:     #raise ValueError("the value is error ")
   ...:     print("it's ok")
   ...: else:
   ...:     print("else")
   ...:
   ...:
  File "<ipython-input-7-dbe923b370cd>", line 4
    else:
       ^
SyntaxError: invalid syntax

# try + except 
# it's work
In [8]: try:
   ...:     #raise ValueError("the value is error ")
   ...:     print("it's ok")
   ...: except Exception as e:
   ...:     print(e)
   ...:
   ...:
   ...:
it's ok

In [9]: try:
   ...:     raise ValueError("the value is error ")
   ...:     print("it's ok")
   ...: except Exception as e:
   ...:     print(e)
   ...:
   ...:
   ...:
the value is error

traceback 和 异常处理

import traceback
import sys

try:
    raise KeyError
except:
    print(sys.exc_info()) # 这是一个 元组 所以我们 可以 用下标访问
    traceback.print_tb(sys.exc_info()[2])

---

tips: 对于新手而言 下面代码 可以多练习。
前面两节 写的 os 模块的很多方法 以及 shutil 都有 使用到。
还有以前写过的 嵌套函数。以及很多老的 知识 。 算是一个回顾。
包括 F-string 以及 循环遍历 if 判断。非常有帮助。

import shutil
import os
import time
import traceback
import sys


def move_files(dir_path, target_path):
    """
    :dir_path: 要移动的文件夹
    :target_path: 移动到那个文件夹
    """
    def loop_move():
        # 嵌套函数
        # 循环遍历 文件
        path_li = os.listdir(dir_path)
        if path_li:
            # 如果列表为空 说明没有文件
            for i in path_li:
                if os.path.splitext(i)[1]:
                    shutil.move(os.path.join(dir_path, i), target_path)
            # 移动文件
            print("++ move complete ++")
            time_end = time.time()
            # 结束时间
            print("move the file of time : ", time_end - time_start, " s")
        else:
            print(f"++ {dir_path} is have not file, complete ++")

    time_start = time.time()  # 开始时间
    if os.path.exists(target_path) and os.path.isdir(target_path):
        # 判断目标文件夹是否存在 和 是否 该目标是否是文件夹
        loop_move()
    else:
        print(f"the dir {target_path} is not exists or not a dir")
        print("ready mkdir")
        try:
            os.mkdir(target_path)
            # 创建 文件夹
        except FileExistsError:
            print(sys.exc_info())
            traceback.print_tb(sys.exc_info()[2])
            print("-" * 20 + "\n")
            # ----------------------------
            print(f"the {target_path} is a file ,not a dir,ready remove")
            os.remove(target_path)
            # 移除文件
            print(f"{target_path} is removed")
            os.mkdir(target_path)
        finally:
            loop_move()

测试自定义异常

我们自己写一个异常类

编写异常类

class AgeError(Exception):  # 继承Exception
    def __init__(self, errorInfo):
        Exception.__init__(self)  # 调用父类构造器
        self.errorInfo = errorInfo

    def __str__(self):
        return str(self.errorInfo)+',年龄错误!!!应该在1-150之间!!!'

测试代码

if __name__ == '__main__':  # 如果为True,则模块是作为独立文件运行,可以执行测试代码!
    age = int(input('输入一个年龄:'))
    if age < 1 or age > 150:
        raise AgeError(age)
    else:
        print('正常的年龄:', age)