函数、参数2

待我称王封你为后i 2021-12-11 07:45 230阅读 0赞

**1、关键字参数和默认值 ，格式：形参=实参/默认参数；使用关键字参数时，不用考虑函数调用参数的顺序，只要形参已经赋值即可；传递的参数数量<=函数中形参的数量**

>>> def pro(name='Lawyer',action='assignment'): \#\#\#\#设定默认参数，如果调用该函数不传递参数，则使用默认值  
　　　　print("%s is %s"%(name,action))

>>> pro(action='drinking',name="Bob") \#\#\#调用函数的时候，使用关键字参数，不用关注参数调用顺序（位置）  
Bob is drinking  
>>> pro() \#\#\#调用函数的时候，不传递参数，使用默认参数  
Lawyer is assignment

>>> pro(name='Alice')\#\#\#只传递一部分参数，另一部分使用默认参数  
Alice is assignment

**2、收集参数\*args  \*收集其余的位置参数组成元组（a，b）；\*\*kwds \*\*收集关键字参数组成字典形式\{\}；**

**\*收集其余的位置参数**

>>> def print\_params(\*params):  
　　　　print(params)

>>> print\_params('Testing')  
('Testing',) \#\#\#只用一个元素的元组后面有一个**，**  
>>> print\_params(1,2,3)   
(1, 2, 3)

>>> print\_params() \#\#\#不传递参数，返回一个空的元组  
()

**\*\*收集关键字参数**

>>> def print\_params\_3(\*\*params):  
print(params)

>>> print\_params\_3(x=1,y=2,z=3)  
\{'x': 1, 'y': 2, 'z': 3\}  
>>> print\_params\_3()  
\{\}

**3、位置参数、关键字参数、\*params、\*\*params的混合使用；位置参数一定要放在关键字参数、收集参数之前**

\#\#\#位置参数一定要放在关键字参数、收集参数之前

>>> def print\_params\_4(x,y,z=3,\*pospar,\*\*keypar):  
print(x,y,z)  
print(pospar)  
print(keypar)

\#\#\#运行顺序：x=1，y=2,关键字参数z=4，其余的位置参数5,6被\*popbar收集成（5,6），关键字参数被\*\*keybar收集成\{'foo': 1, 'bar': 2\}  
>>> print\_params\_4(1,2,4,5,6,foo=1,bar=2)  
1 2 4  
(5, 6)  
\{'foo': 1, 'bar': 2\}

**4、改写store函数，之前store函数只能接受处理一个参数；现在改写成处理多个参数**

def init(data):
        data['first'] = {}
        data['middle'] = {}
        data['third'] = {}
    
    def lookup(data,label,name):
        return data[label][name]
    
    def store(data,*full_names):
        for full_name in full_names:
            names = full_name.split()
            if len(names)==2:
                names.insert(1,'')
            labels = ['first','middle','third']
            for label,name in zip(labels,names):
                try:
                    people = lookup(data,label,name)
                except KeyError as err:
                    print("KeyError:"+str(err))
                    people = None
                finally:
                    if people:
                        data[label][name].append(full_name)
                    else:
                        data[label][name]=full_name
        return data
    
    if __name__ == '__main__':
        mynumbs_1 = {}
        mynumbs_2 = {}
        mynumbs_3 = {}
        init(mynumbs_1)
        init(mynumbs_2)
        init(mynumbs_3)
        mynumbs_1=store(mynumbs_1, 'Li zhang yang')###传入一个full_names参数，*full_names将后面的位置参数组合成（'Li zhang yang'，）

###传入两个full_names参数，*full_names将后面的两个位置参数组合成（'Li zhang yang','zhang hang hang'）

mynumbs_2 = store(mynumbs_2, 'Li zhang yang','zhang hang hang')

full_names = ('Li zhang yang', 'zhang hang hang')###类似*full_names的反应用
     mynumbs_3 = store(mynumbs_3, *full_names)
        print(mynumbs_1,'\n',mynumbs_2,'\n',mynumbs_3)
        mynumbs_4 =store(mynumbs_3,('Li zhang yang', 'zhang hang hang')) ###不能直接传tuple作为参数，会报错因为*会把后面这个位置参数组合成（('Li zhang yang', 'zhang hang hang')，）组成了set序列 遍历full_names时('Li zhang yang', 'zhang hang hang')会被当成一个元素处理，tuple元素没有split属性

![1360913-20190512205357260-822041295.png][]

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转载于:https://www.cnblogs.com/t-ae/p/10853682.html

[1360913-20190512205357260-822041295.png]: /images/20211211/77c5f6fb0df8417d9bbd58198a2c170a.png