【python】错误/异常处理,调试,测试

try:
print('try')
r=10/2
print('result is:',r)
#发生错误,会执行这部分
except ValueError as e:
print('ValueError:', e)
except ZeroDivisionError as e:
print('ZeroDivisionError:', e)
finally: #无论有没有发生错误,都执行
print("finally")

Python的错误其实也是class,所有的错误类型都继承自BaseException

捕获错误的类型,也涵盖其子类

https://docs.python.org/3/library/exceptions.html#exception-hierarchy

一般不知道具体的错误,就可以写最外层的错误类,Exception

except Exception as e:
print('aaa:',e)

调用堆栈:

错误演示:

def foo(s):
return 10 / int(s) def bar(s):
return foo(s) * 2 def main():
bar('') main()
Traceback (most recent call last):        #出错信息追踪
File "E:/pyfile/httpauto/ceshi.py", line 10, in <module>
main()
File "E:/pyfile/httpauto/ceshi.py", line 8, in main
bar('')
File "E:/pyfile/httpauto/ceshi.py", line 5, in bar
return foo(s) * 2
File "E:/pyfile/httpauto/ceshi.py", line 2, in foo
return 10 / int(s)
ZeroDivisionError: division by zero

记录错误:

如果不容错的话,出错了程序会自动断掉,然后用堆栈的方式,打印出错误信息。如果容错,就可以打出错误并且不影响程序继续执行

调试

方法一:print()把变量一个个打印出来

方法二:增加断言assert

def foo(s):
n=int(s)
assert n!=0,'n is zero!' #断言为true,继续执行
return 10/n def main():
foo('') main()

方法三:替换为logging

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