学习心得2020.08.30

032异常处理

file_name=input('请输入需要打开的文件名:')
f=open(file_name)
print('文件的内容是：')
for each_line in f:
    print(each_line)

>>> my_list=['小甲鱼是帅哥']
>>> assert len(my_list)>0
>>> my_list.pop()
'小甲鱼是帅哥'
>>> assert len(my_list)>0
Traceback (most recent call last):
  File "<pyshell#3>", line 1, in <module>
    assert len(my_list)>0
AssertionError
>>> my_list.fishc
Traceback (most recent call last):
  File "<pyshell#4>", line 1, in <module>
    my_list.fishc
AttributeError: 'list' object has no attribute 'fishc'
>>> my_list=[1,2,3]
>>> my_lsit[3]
Traceback (most recent call last):
  File "<pyshell#6>", line 1, in <module>
    my_lsit[3]
NameError: name 'my_lsit' is not defined
>>> my_list[2]
3
>>> my_dict={'one':1,'two':2,'three':3}
>>> my_dict['one']
1
>>> my_dict['two']
2
>>> my_dict['four']
Traceback (most recent call last):
  File "<pyshell#11>", line 1, in <module>
    my_dict['four']
KeyError: 'four'
>>> 1+'1'
Traceback (most recent call last):
  File "<pyshell#12>", line 1, in <module>
    1+'1'
TypeError: unsupported operand type(s) for +: 'int' and 'str'

033异常检测

• try-except语句
  try:
  检测范围
  except Exception[as reason]:
  出现异常(Exception)后的处理代码

try:
    sum=1+'1'
    f=open('我为什么是一个文件.txt')
    print(f.read())
    f.close()
except OSError as reason:
    print('文件出错啦,出错的原因是：'+str(reason))
except TypeError as reason:
    print('类型出错啦,出错的原因是：'+str(reason))

• try-finally语句
  try:
  检测范围
  except Exception[as reason]:
  出现异常(Exception)后的处理代码
  finally:
  无论如何都会被执行的代码

try:
    f=open('我为什么是一个文件.txt','w')
    print(f.write('我存在了！'))
    sum=1+'1'
except (OSError,TypeError):
    print('文件出错啦')
finally:
    f.close()

• raise语句
  可以在其中添加解释异常原因的语句

>>> raise ZeroDivisionError('除数为零的异常')
Traceback (most recent call last):
  File "<pyshell#13>", line 1, in <module>
    raise ZeroDivisionError('除数为零的异常')
ZeroDivisionError: 除数为零的异常