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多个函数参数
内容： 在 Python 中，每个函数接受的参数数量是预定义的，如果正常声明的话，如下所示：
python
def myfunction(first, second, third):
# 对三个变量进行某些操作
...
可以声明接收可变数量参数的函数，使用以下语法：
python
def foo(first, second, third, *therest):
print("First: %s" % first)
print("Second: %s" % second)
print("Third: %s" % third)
print("And all the rest... %s" % list(therest))
“therest”变量是一个变量列表，它接收所有在前三个参数之后传递给“foo”函数的参数。因此调用foo(1, 2, 3, 4, 5)将输出：
```python def foo(first, second, third, *therest): print("First: %s" %(first)) print("Second: %s" %(second)) print("Third: %s" %(third)) print("And all the rest... %s" %(list(therest)))
foo(1, 2, 3, 4, 5) ```
也可以通过关键字传递函数参数，这样参数的顺序就不重要了，使用以下语法。以下代码提供以下输出：
输出：
The sum is: 6
Result: 1
```python def bar(first, second, third, **options): if options.get("action") == "sum": print("The sum is: %d" %(first + second + third))
if options.get("number") == "first":
return first
result = bar(1, 2, 3, action = "sum", number = "first") print("Result: %d" %(result)) ```
“bar”函数接受3个参数。如果接收到一个附加的“action”参数，并指示对数字进行求和，那么总和将被打印出来。或者，如果传递给函数的“number”参数的值等于“first”，则函数还会返回第一个参数。
练习
填充 foo 和 bar 函数，使它们可以接收可变数量的参数（3个或更多）。
foo 函数必须返回接收到的额外参数的数量。
如果带有关键字 magicnumber 的参数等于7，bar 函数必须返回 True，否则返回 False。
# edit the functions prototype and implementation
def foo(a, b, c):
pass
def bar(a, b, c):
pass
# test code
if foo(1, 2, 3, 4) == 1:
print("Good.")
if foo(1, 2, 3, 4, 5) == 2:
print("Better.")
if bar(1, 2, 3, magicnumber=6) == False:
print("Great.")
if bar(1, 2, 3, magicnumber=7) == True:
print("Awesome!")
# edit the functions prototype and implementation
def foo(a, b, c, *args):
return len(args)
def bar(a, b, c, **kwargs):
return kwargs["magicnumber"] == 7
# test code
if foo(1, 2, 3, 4) == 1:
print("Good.")
if foo(1, 2, 3, 4, 5) == 2:
print("Better.")
if bar(1, 2, 3, magicnumber=6) == False:
print("Great.")
if bar(1, 2, 3, magicnumber=7) == True:
print("Awesome!")
test_output_contains("Good.")
test_output_contains("Better.")
test_output_contains("Great.")
test_output_contains("Awesome!")
success_msg("Great work!")
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