即使你现在想不出它的用途，你可以打赌它一定会有用处的。下面是一个没有想象力的例子:

其他:

a = [1,2,3]
try:
    something = a[2]
except IndexError:
    print("out of bounds")
else:
    print(something)

没有其他的:

try:
    something = a[2]
except IndexError:
    print("out of bounds")

if "something" in locals():
    print(something)

在这里，如果没有抛出错误，则定义了变量something。您可以在try块之外删除它，但如果定义了变量，则需要进行一些混乱的检测。

try:
    statements # statements that can raise exceptions
except:
    statements # statements that will be executed to handle exceptions
else:
    statements # statements that will be executed if there is no exception

例子:

try:
    age=int(input('Enter your age: '))
except:
    print ('You have entered an invalid value.')
else:
    if age <= 21:
        print('You are not allowed to enter, you are too young.')
    else:
        print('Welcome, you are old enough.')

输出:

>>> 
Enter your age: a
You have entered an invalid value.
>>> RESTART
>>> 
Enter your age: 25
Welcome, you are old enough.
>>> RESTART
>>> 
Enter your age: 13
You are not allowed to enter, you are too young.
>>> 

复制自:https://geek-university.com/python/the-try-except-else-statements/

错误和异常#处理异常- docs.python.org

The try ... except statement has an optional else clause, which, when present, must follow all except clauses. It is useful for code that must be executed if the try clause does not raise an exception. For example: for arg in sys.argv[1:]: try: f = open(arg, 'r') except IOError: print 'cannot open', arg else: print arg, 'has', len(f.readlines()), 'lines' f.close() The use of the else clause is better than adding additional code to the try clause because it avoids accidentally catching an exception that wasn’t raised by the code being protected by the try ... except statement.

else:块令人困惑并且(几乎)毫无用处。它也是for和while语句的一部分。

实际上，即使在if语句中，else:也可能被滥用，造成非常难以发现的错误。

考虑这一点。

   if a < 10:
       # condition stated explicitly
   elif a > 10 and b < 10:
       # condition confusing but at least explicit
   else:
       # Exactly what is true here?
       # Can be hard to reason out what condition is true

三思而后行。这通常是个问题。除非在if语句中，否则避免使用它，即使在if语句中，也要考虑记录else-条件，使其显式。

我将添加另一个用例，在处理DB会话时看起来很直接:

    # getting a DB connection 
    conn = db.engine.connect()

    # and binding to a DB session
    session = db.get_session(bind=conn)

    try:
        # we build the query to DB
        q = session.query(MyTable).filter(MyTable.col1 == 'query_val')

        # i.e retrieve one row
        data_set = q.one_or_none()

        # return results
        return [{'col1': data_set.col1, 'col2': data_set.col2, ...}]

    except:
        # here we make sure to rollback the transaction, 
        # handy when we update stuff into DB
        session.rollback()
        raise

    else:
        # when no errors then we can commit DB changes
        session.commit()

    finally:
        # and finally we can close the session
        session.close()

下面是我喜欢使用这种模式的另一个地方:

 while data in items:
     try
        data = json.loads(data)
     except ValueError as e:
        log error
     else:
        # work on the `data`