当电脑中没有a.txt这个文件时，
try:
f=open('a.txt','r')
except TypeError:
print('no file.')
输出
====================== RESTART: C:/Python34/xuexi/1.py ======================Traceback (most recent call last):
File "C:/Python34/xuexi/1.py", line 2, in
f=open('a.txt','r')
FileNotFoundError: [Errno 2] No such file or directory: 'a.txt'
During handling of the above exception, another exception occurred:
Traceback (most recent call last): File "C:/Python34/xuexi/1.py", line 3, inexcept typeerror:
NameError: name 'typeerror' is not defined
将TypeError改为FileNotFoundError
try:
f=open('a.txt','r')
except TypeError:
print('no file.')
输出
no file.
>>>
当文件存在时,输出为2.txt的内容
try:
f=open('2.txt','r')
print(f.read())
f.close()
except TypeError:
print('no file.')
输出
ID
age
abc
>>>
当文件存在时，
try:
f=open('2.txt','r')
print(f.read())
except IOError:
print('no file.')
except TypeError:
print('type error.')
except:
print("other error.")
else:
print("file exist")
finally:
print("done")
输出
ID
age
abc
file exist
done
>>>
当文件不存在时，
try:
f=open('2q.txt','r')
print(f.read())
except IOError:
print('no file.')
except TypeError:
print('type error.')
except:
print("other error.")
else:
print("file exist")
finally:
print("done")
输出
no file.
done
>>>
import traceback
try:
a=b
b=c
except:
f=open('log.txt','a') #a附加
f.flush() #flush 写入缓存
traceback.print_exc(file=f)
finally:
print("save log.")
f.close()
输出
save log.
>>>
a=None
try:
if a=='None':
raise Exception("not object") #不管有没有，都定义为异常
print("a is null")
except:
print("error")
finally:
print("Done")
输出
Done
>>>
import time
try:
f=open('1.txt')
while True:
line =f.readlines() #当有1.txt这个文件时，输出结果
if len(line)==0: #如果行等于0
break
time.sleep(2) #等2秒
print(line)
finally:
f.close()
输出
['ID\n', 'age\n', 'aaa']
>>>
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