python - "raise"和 "raise e"之间的区别？

Question

在python中，raise和raise e在except block 中有区别吗？

dis 向我显示不同的结果，但我不知道这是什么意思。

两者的最终行为是什么？

import dis
def a():
    try:
        raise Exception()
    except Exception as e:
        raise


def b():
    try:
        raise Exception()
    except Exception as e:
        raise e

dis.dis(a)
# OUT:   4           0 SETUP_EXCEPT            13 (to 16)
# OUT:   5           3 LOAD_GLOBAL              0 (Exception)
# OUT:               6 CALL_FUNCTION            0
# OUT:               9 RAISE_VARARGS            1
# OUT:              12 POP_BLOCK           
# OUT:              13 JUMP_FORWARD            22 (to 38)
# OUT:   6     >>   16 DUP_TOP             
# OUT:              17 LOAD_GLOBAL              0 (Exception)
# OUT:              20 COMPARE_OP              10 (exception match)
# OUT:              23 POP_JUMP_IF_FALSE       37
# OUT:              26 POP_TOP             
# OUT:              27 STORE_FAST               0 (e)
# OUT:              30 POP_TOP             
# OUT:   7          31 RAISE_VARARGS            0
# OUT:              34 JUMP_FORWARD             1 (to 38)
# OUT:         >>   37 END_FINALLY         
# OUT:         >>   38 LOAD_CONST               0 (None)
# OUT:              41 RETURN_VALUE        
dis.dis(b)
# OUT:   4           0 SETUP_EXCEPT            13 (to 16)
# OUT:   5           3 LOAD_GLOBAL              0 (Exception)
# OUT:               6 CALL_FUNCTION            0
# OUT:               9 RAISE_VARARGS            1
# OUT:              12 POP_BLOCK           
# OUT:              13 JUMP_FORWARD            25 (to 41)
# OUT:   6     >>   16 DUP_TOP             
# OUT:              17 LOAD_GLOBAL              0 (Exception)
# OUT:              20 COMPARE_OP              10 (exception match)
# OUT:              23 POP_JUMP_IF_FALSE       40
# OUT:              26 POP_TOP             
# OUT:              27 STORE_FAST               0 (e)
# OUT:              30 POP_TOP             
# OUT:   7          31 LOAD_FAST                0 (e)
# OUT:              34 RAISE_VARARGS            1
# OUT:              37 JUMP_FORWARD             1 (to 41)
# OUT:         >>   40 END_FINALLY         
# OUT:         >>   41 LOAD_CONST               0 (None)
# OUT:              44 RETURN_VALUE        

Answer 1

两种形式生成的回溯存在差异。

使用raise，这段代码:

try:
   int("hello")
except ValueError as e:
   raise

提供以下回溯:

Traceback (most recent call last):
  File "myfile.py", line 2, in <module>
    int("hello")
ValueError: invalid literal for int() with base 10: 'hello'

使用raise e如下:

try:
   int("hello")
except ValueError as e:
   raise e

给出以下回溯

Traceback (most recent call last):
  File "myfile.py", line 4, in <module>
    raise e
ValueError: invalid literal for int() with base 10: 'hello'

不同之处在于，在 raise 情况下，引用异常原始源的正确行在回溯中引用，但在 raise e 情况下，回溯引用 raise e 行而不是原始原因。

因此，我建议始终使用 raise 而不是 raise e。