Pyhon参数介绍

• 关键字参数

def func(name='zhangsan', age=18):
    print("我的名字是{0}，今年{1}岁".format(name,age))

func() #姓名、年龄均为默认值zhansan和18
func(age=20) #姓名为默认值zhangsan，年龄为20
func(name='lisi',age=28) #姓名和年龄分别为lisi和28

• 收集参数

def func(*args):#定义形式参数args，以*开头，表示参数收集，可以接受任意多个参数，都打包装入元组args中，可以传空
    for item in args: #遍历元组args
        print(item)

func(1,2,3,'zhangsan','lisi',4,5)
func(‘huawei’,'xiaomi','sanxing')

•  关键字收集参数

def student(**kwargs): #以**开头的参数表示为关键字收集参数，可以传空
    print(type(kwargs))  #关键字参数的类型为字典（即key,value对）
    for k,v in kwargs.items(): #遍历字典
        print(k,"...",v)

student(name='zhangsan', age=19, addr='peking',  worker='teacher')
student(name='lisi', age=22)

•  普通参数、收集参数、关键字参数的调研顺序

def stu(name, age, *args, hobby='none',**kwargs): #注意顺序为依次：普通参数、收集参数、关键字参数、关键字收集参数
    print("my name is {0}, i'm {1} years old".format(name,age))
    if hobby=='none':
        print("sorry, i've no hobbies")
    else:
        print("my hobby is {0}".format(hobby))

    print("*"*20)
    for item in args:
        print(item)

    print("#"*20)
    for k,v in kwargs.items():
        print(k,"...",v)

name="zhangsan"
age=19
stu(name, age) #只传入普通参数
stu(name, age, hobby="swim") #传入普通参数、关键字参数
stu(name, age, "lisi", "wangwu", hobby="swim", hobby1="cook", hobby2="basketball") #传入普通参数、收集参数、关键字参数、关键字手机参数，注意顺序！

 输出为

my name is zhangsan, i'm 19 years old
sorry, i've no hobbies
********************
####################
my name is zhangsan, i'm 19 years old
my hobby is: swim
********************
####################
my name is zhangsan, i'm 19 years old
my hobby is: swim
********************
lisi
wangwu
####################
hobby1 ... cook
hobby2 ... basketball

•  收集参数、关键字收集参数的解包

def func(*args):
    n = 0
    for item in args:
        print("loop {0}".format(n))
        print(item)
        n += 1

l = [1,2,3,'zhangsan','lisi',4,5]
func(l) #未解包，此时for循环进循环依次，且打印的item直接为整个数组
func(*l) #加上*进行解包，for循环遍历数组中的每个元素

 同理，对关键字收集参数也可以进行解包，使用两个*号：**