【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('0')

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('0')
  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('0')

main()

方法三：替换为logging