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2017-8-7 python args and kwargs

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*args

传递一个非键值对的可变数量的参数列表给一个函数。

def test_var_args(f_arg, *argv):
    print("first normal arg:", f_arg)
    for arg in argv:
        print("another arg through *argv:", arg)

test_var_args('yasoob', 'python', 'eggs', 'test')

output:

first normal arg: yasoob

another arg through *argv: python

another arg through *argv: eggs

another arg through *argv: test

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### `**kwargs`:
> 传递不定长度的键值对(字典), 作为参数传递给一个函数(即传递带名字的参数)。
```python
def greet_me(**kwargs):
    for key, value in kwargs.items():
        print("{0} == {1}".format(key, value))

>>> greet_me(name="yasoob")
name == yasoob

注意:

不是必须写成*args**kwargs,只有变量前面的 *(星号)才是必须的;可以写成*var**vars,写成*args**kwargs只是一个通俗的命名约定; *args: 顺序不能变动;**kwargs:可以根据键指定顺序。

def test_args_kwargs(arg1, arg2, arg3):
    print("arg1:", arg1)
    print("arg2:", arg2)
    print("arg3:", arg3)

首先使用 *args

args = ("two", 3, 5) test_args_kwargs(*args) arg1: two arg2: 3 arg3: 5

现在使用 **kwargs:

kwargs = {"arg3": 3, "arg2": "two", "arg1": 5} test_args_kwargs(**kwargs) arg1: 5 arg2: two arg3: 3