python -Exception

#系统异常信息捕获   try....except...as....else  、try....except...as....finally

try:
#输入文件名称，打开文件
    filename=input("input fileName:")
    open("%s.txt"%filename)
#BaseException 后加as可获取系统异常信息
except BaseException as msg:
    print(msg)
#没有异常就打印else

else:
    print(filename)
#不论是否有异常都执行finally内容

finally:
    print("the end!")

Try是执行过程中捕获异常，raise是先定义一个标准，不符合条件就抛出异常（raise必须接python标准异常类，如

ZeroDivisionError）

def div(x,y):
    if y==0:
        raise ZeroDivisionError("zeroisnotallow")
    return x/y
try:
    div(8,0)
except BaseException as msg:
    print(msg)