Python基础学习（六）-----函数应用

一. 参数

1. 匹配

1. 位置匹配
2. 关键字匹配

def func(a,b,c):
    print(a,b,c)

func(c=1,a=2,b=3)

3. 默认值（调用时省略传值）

def func(a,b=2,c=3):
    print(a,b,c)

func(1)

4. *args 任意数量参数

def avg(*scores):
    return sum(scores)/len(scores)

scores=(98.2,88.4,70,65)
result=avg(*scores)
print(result)

5. **kwargs 字典

def display_employee(**employee):
    print(employee)

display_employee(name='tom',age=22,job='dev')

二. Lambda表达式

1. 定义匿名函数

2. 基本表达式

f= lambda name: print(name)
f2 = lambda x,y: x+y

f('tom')
print(f2(5,3))

def hello_chinese(name):
    print("你好:",name)

def hello_english(name):
    print('hello:',name)

hello = hello_chinese
hello = lambda name: print('hello:',name)

hello('tom')

def hello_chinese(name):
    print('hello:',name)

def hello_english(name):
    print('hello:',name)

def hello_japanese(name):
    print('hello:',name)

def hello(action,name): #action是一个函数
    action(name)

hello(hello_chinese,'Tom')
hello(lambda name: print('hhh',name),'Tom')

三. 高级工具

1. map函数，可迭代对象

l = list(range(1,21))

res=[]

def add_number(x):
    return x+5

#1. 使用循环
for x in l:
    res.append(x+5)

#2. 使用推导
res=[x+5 for x in l]

#3.map()
res = list(map(add_number,l))
res = list(map(lambda n: n**2,l))

print(res)

2. filter函数，可迭代对象(不是list）

l = list(range(1,11))

def even_number(x):
    return x%2 == 0

res = filter(even_number,l)
res = filter(lambda n : n%2 ==0,l)
res = [x for x in l if x%2 == 0]

for n in res:
    print(n,end=' ')