python-3.x - 即使在任何时候都不访问e，都将异常定义为变量(作为e除外的异常)的最佳实践吗？

Question

如果我们不使用e异常不做任何事情，那是更好的做法:

except Exception:
    pass

要么

except Exception as e:
    pass

我很好奇，即使我们以后不访问 except Exception as e:对象，编写 e是否是最佳实践。

Answer 1

如果您不打算使用该异常，则不应命名该异常。

您实际上可以从反汇编中看到except Error:方法更有效，因为它不必创建e变量:

>>> def foo1():
...     try:
...         1 / 0
...     except ZeroDivisionError:
...         pass
...
>>> def foo2():
...     try:
...         1 / 0
...     except ZeroDivisionError as e:
...         pass
...
>>> import dis
>>> dis.dis(foo1)
  2           0 SETUP_EXCEPT            12 (to 14)

  3           2 LOAD_CONST               1 (1)
              4 LOAD_CONST               2 (0)
              6 BINARY_TRUE_DIVIDE
              8 POP_TOP
             10 POP_BLOCK
             12 JUMP_FORWARD            20 (to 34)

  4     >>   14 DUP_TOP
             16 LOAD_GLOBAL              0 (ZeroDivisionError)
             18 COMPARE_OP              10 (exception match)
             20 POP_JUMP_IF_FALSE       32
             22 POP_TOP
             24 POP_TOP
             26 POP_TOP

  5          28 POP_EXCEPT
             30 JUMP_FORWARD             2 (to 34)
        >>   32 END_FINALLY
        >>   34 LOAD_CONST               0 (None)
             36 RETURN_VALUE
>>> dis.dis(foo2)
  2           0 SETUP_EXCEPT            12 (to 14)

  3           2 LOAD_CONST               1 (1)
              4 LOAD_CONST               2 (0)
              6 BINARY_TRUE_DIVIDE
              8 POP_TOP
             10 POP_BLOCK
             12 JUMP_FORWARD            34 (to 48)

  4     >>   14 DUP_TOP
             16 LOAD_GLOBAL              0 (ZeroDivisionError)
             18 COMPARE_OP              10 (exception match)
             20 POP_JUMP_IF_FALSE       46
             22 POP_TOP
             24 STORE_FAST               0 (e)
             26 POP_TOP
             28 SETUP_FINALLY            4 (to 34)

  5          30 POP_BLOCK
             32 LOAD_CONST               0 (None)
        >>   34 LOAD_CONST               0 (None)
             36 STORE_FAST               0 (e)
             38 DELETE_FAST              0 (e)
             40 END_FINALLY
             42 POP_EXCEPT
             44 JUMP_FORWARD             2 (to 48)
        >>   46 END_FINALLY
        >>   48 LOAD_CONST               0 (None)
             50 RETURN_VALUE

任何阅读您的代码的人都可以立即清楚地知道，如果您不命名该异常，那么您就不会对其进行任何操作(记录它，更改它等)。