python - 相当于 try/except/finally 语句

Question

Python 简介

A try / except / finally statement, such as:

try:
    ...guarded clause...
except ...expression...:
    ...exception handler code...
finally:
    ...clean-up code...

is equivalent to the nested statement:

try:
    try:
        ...guarded clause...
    except ...expression...:
        ...exception handler code...
finally:
    ...clean-up code...

1. 为什么它相当于嵌套表单？

2. 是否可以写成与不带finally的形式等价？

   是否相当于

   try:
       ...guarded clause...
   except ...expression...:
       ...exception handler code...
       ...clean-up code...
   ...clean-up code...
   

谢谢。

Answer 1

1. 因为这就是它的定义方式。因为以这种方式定义它是有用且标准的，并且因为没有其他有用的方法来定义它。

2. 是的，但不是你这样做的方式。

   try:
       do_stuff()
   except OneProblem:
       handle_it()
   except DifferentProblem:
       handle_that()
   finally:
       cleanup()
   

   相当于

   try:
       try:
           do_stuff()
       except OneProblem:
           handle_it()
       except DifferentProblem:
           handle_that()
   except:
       # Clean up if an unhandled exception happened, then restore the exception.
       cleanup()
       raise
   # Also clean up if we're not propagating an exception.
   cleanup()
   

就清理而言，总是会发生并且不会发生两次，尽管异常链接和回溯之类的行为可能会有所不同。