对python中的try、except、finally 执行顺序详解_Python

如下所示：

									def test1():

									  try:

									   print('to do stuff')

									   raise Exception('hehe')

									   print('to return in try')

									   return 'try'

									 except Exception:

									   print('process except')

									   print('to return in except')

									   return 'except'

									 finally:

									   print('to return in finally')

									   return 'finally'

									test1Return = test1()

									print('test1Return : ' + test1Return)

输出：

				?

									to do stuff

									process except

									to return in except

									to return in finally

									test1Return : finally

在 try 中 raise一个异常，就立刻转入 except 中执行，在except 中遇到 return 时，就强制转到 finally 中执行，在 finally 中遇到 return 时就返回

				?

									def test2():

									  try:

									   print('to do stuff')

									   print('to return in try')

									   return 'try'

									 except Exception:

									   print('process except')

									   print('to return in except')

									   return 'except'

									 finally:

									   print('to return in finally')

									   return 'finally'

									test2Return = test2()

									print('test1Return : ' + test2Return)

输出：

				?

									to do stuff

									to return in try

									to return in finally

									test2Return : finally

这里在 try 中没有抛出异常，因此不会转到 except 中，但是在try 中遇到return时，也会立即强制转到finally中执行，并在finally中返回

test1和test2得到的结论：

无论是在try还是在except中，遇到return时，只要设定了finally语句，就会中断当前的return语句，跳转到finally中执行，如果finally中遇到return语句，就直接返回，不再跳转回try/excpet中被中断的return语句

				?

									def test3():

									  i = 0

									 try:

									   i += 1

									 print('i in try : %s'%i)

									   raise Exception('hehe')

									 except Exception:

									   i += 1

									 print('i in except : %s'%i)

									   return i

									   finally:

									   i += 1

									 print ('i in finally : %s'%i )

									print('test3Return : %s'% test3())

输出：

				?

									i in try : 1

									i in except : 2

									i in finally : 3

									test3Return : 2

									def test4():

									  i = 0

									 try:

									   i += 1

									 return i

									  finally:

									   i += 1

									 print ('i in finally : %s'%i )

									print('test4Return : %s' % test4())

输出

				?

									i in finally : 2

									test4Return : 1

test3和test4得到的结论：

在except和try中遇到return时，会锁定return的值，然后跳转到finally中，如果finally中没有return语句，则finally执行完毕之后仍返回原return点，将之前锁定的值返回(即finally中的动作不影响返回值)，如果finally中有return语句，则执行finally中的return语句。

				?

									def test5():

									  for i in range(5):

									   try:

									     print('do stuff %s'%i)

									     raise Exception(i)

									   except Exception:

									     print('exception %s'%i)

									     continue

									 finally:

									     print('do finally %s'%i)

									test5()

输出

				?

									do stuff 0

									exception 0

									do finally 0

									do stuff 1

									exception 1

									do finally 1

									do stuff 2

									exception 2

									do finally 2

									do stuff 3

									exception 3

									do finally 3

									do stuff 4

									exception 4

									do finally 4