抛出异常

raise 语句 允许强制发生指定的异常。

raise NameError('HiThere')

---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

<ipython-input-1-72c183edb298> in <module>
----> 1 raise NameError('HiThere')


NameError: HiThere

如果你需要确定是否引发了异常但不打算处理它，则可以使用更简单的 raise 语句形式重新引发异常:

try:
    raise NameError('HiThere')
except NameError:
    print('An exception flew by!')
    raise

An exception flew by!


---------------------------------------------------------------------------

NameError                                 Traceback (most recent call last)

<ipython-input-2-bf6ef4926f8c> in <module>
      1 try:
----> 2     raise NameError('HiThere')
      3 except NameError:
      4     print('An exception flew by!')
      5     raise


NameError: HiThere