异常处理

我们常常想在没有触发异常的时候执⾏⼀些代码，这可以很轻松地通过⼀个else从句来达到。
有⼈也许问了：如果你只是想让⼀些代码在没有触发异常的情况下执⾏，为啥你不直接把代码放在try⾥⾯呢？
回答是，那样的话这段代码中的任意异常都还是会被try捕获，⽽你并不⼀定想要那样。
⼤多数⼈并不使⽤else从句，⽽且坦率地讲我⾃⼰也没有⼤范围使⽤。
这⾥是个例⼦：

try:
	print('I am sure no exception is going to occur!') 
except Exception: 
    print('exception') 
else:
    # 这⾥的代码只会在try语句⾥没有触发异常时运⾏, 
    # 但是这⾥的异常将 *不会* 被捕获 
    print('This would only run if no exception occurs. And an error here ' 'would NOT be caught.')
finally: 
    print('This would be printed in every case.')

输出：
I am sure no exception is going to occur!
This would only run if no exception occurs. And an error here would NOT be
caught.
This would be printed in every case.