python中 try、except、finally 的执行顺序(转)

to do stuff
process except
to return in except
to return in finally
test1Return : finally

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)

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())

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

test5得到的结论：

在一个循环中，最终要跳出循环之前，会先转到finally执行，执行完毕之后才开始下一轮循环