我想知道在Python中指示无效参数组合的最佳实践。我遇到过一些情况，你有一个这样的函数:
def import_to_orm(name, save=False, recurse=False):
"""
:param name: Name of some external entity to import.
:param save: Save the ORM object before returning.
:param recurse: Attempt to import associated objects as well. Because you
need the original object to have a key to relate to, save must be
`True` for recurse to be `True`.
:raise BadValueError: If `recurse and not save`.
:return: The ORM object.
"""
pass
唯一的麻烦是每个包都有自己的BadValueError，通常略有不同。我知道在Java中存在Java .lang. illegalargumentexception——每个人都将在Python中创建自己的BadValueErrors，这是很好理解的，还是有其他的首选方法?
这取决于论点的问题是什么。
如果实参的类型错误，则引发TypeError。例如，当你得到一个字符串而不是布尔值。
if not isinstance(save, bool):
raise TypeError(f"Argument save must be of type bool, not {type(save)}")
但是请注意，在Python中我们很少做这样的检查。如果这个论证真的是无效的，一些更深层的功能可能会替我们抱怨。如果我们只检查布尔值，也许一些代码用户稍后会给它一个字符串，因为他们知道非空字符串总是True。这也许能救他一命。
如果实参的值无效，则引发ValueError。这似乎更适合你的情况:
if recurse and not save:
raise ValueError("If recurse is True, save should be True too")
或者在这个特定的情况下，使用recurse的True值暗示save的True值。因为我认为这是从错误中恢复，所以您可能还想在日志中抱怨。
if recurse and not save:
logging.warning("Bad arguments in import_to_orm() - if recurse is True, so should save be")
save = True
我认为最好的处理方法是python本身处理它的方式。Python引发TypeError。例如:
$ python -c 'print(sum())'
Traceback (most recent call last):
File "<string>", line 1, in <module>
TypeError: sum expected at least 1 arguments, got 0
我们的初级开发人员刚刚在谷歌上搜索“python异常错误参数”时发现了这个页面，我很惊讶，自这个问题被提出以来的十年里，这个明显的(对我来说)答案从未被提出过。
You would most likely use ValueError (raise ValueError() in full) in this case, but it depends on the type of bad value. For example, if you made a function that only allows strings, and the user put in an integer instead, you would you TypeError instead. If a user inputted a wrong input (meaning it has the right type but it does not qualify certain conditions) a Value Error would be your best choice. Value Error can also be used to block the program from other exceptions, for example, you could use a ValueError to stop the shell form raising a ZeroDivisionError, for example, in this function:
def function(number):
if not type(number) == int and not type(number) == float:
raise TypeError("number must be an integer or float")
if number == 5:
raise ValueError("number must not be 5")
else:
return 10/(5-number)
附注:python内置异常列表，请点击此处:
https://docs.python.org/3/library/exceptions.html(这是官方的python数据库)
