如何循环函数参数 [英] How to iterate over function arguments

问题描述

我有一个Python函数接受几个字符串参数 DEF美孚（A，B，C）：和字符串串联它们。
我想遍历所有的函数参数来检查他们不无。如何可以做到？
是否有一个快速的方法来转换成无为？

I have a Python function accepting several string arguments def foo(a, b, c): and concatenating them in a string. I want to iterate over all function arguments to check they are not None. How it can be done? Is there a quick way to convert None to ""?

感谢。

推荐答案

当地人（） 可能是你的朋友在这里，如果你把它的第一件事就是你的函数。

locals() may be your friend here if you call it first thing in your function.

示例1

>>> def fun(a, b, c):
...     d = locals()
...     e = d
...     print e
...     print locals()
... 
>>> fun(1, 2, 3)
{'a': 1, 'c': 3, 'b': 2}
{'a': 1, 'c': 3, 'b': 2, 'e': {...}, 'd': {...}}

例2

>>> def nones(a, b, c, d):
...     arguments = locals()
...     print 'The following arguments are not None: ', ', '.join(k for k, v in arguments.items() if v is not None)
... 
>>> nones("Something", None, 'N', False)
The following arguments are not None:  a, c, d

答

>>> def foo(a, b, c):
...     return ''.join(v for v in locals().values() if v is not None)
... 
>>> foo('Cleese', 'Palin', None)
'CleesePalin'

更新

'例1'的亮点，我们可能有一些额外的工作要做，如果你的参数的顺序是作为字典按返回当地人重要（）（或瓦尔（））是无序的。以上且功能不带数字处理非常优雅。因此，这里有一对夫妇改进的：

'Example 1' highlights that we may have some extra work to do if the order of your arguments is important as the dict returned by locals() (or vars()) is unordered. The function above also doesn't deal with numbers very gracefully. So here are a couple of refinements:

>>> def foo(a, b, c):
...     arguments = locals()
...     return ''.join(str(arguments[k]) for k in sorted(arguments.keys()) if arguments[k] is not None)
... 
>>> foo(None, 'Antioch', 3)
'Antioch3'

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