python基础--函数

1、定义函数

# 全局变量和局部变量名字相同
str = "aaa" # 定义了一个全局变量
def myPrint():
    #global str #：使用global对一个全局变量的声明
    str = "bbb"
    print(str)
    
myPrint()  # 结果：bbb
print(str) # 结果：aaa

2、缺省参数：

def myPrint(name, age = 10):
    print(name)
    print(age)
    
myPrint("zs", 20)
myPrint("zs")
print("=" * 10)
myPrint(name = "zs", age = 30)
myPrint(name = "zs")

3、不定长参数

def myPrint(a, *params):
    print(a)
    print(params) # (10, 20, 30)
    
myPrint("zs", 10, 20, 30)

def myPrint(a, **params):
    print(a)
    print(params)
    for i in params:
        print(i)
    
myPrint("zs", name='zs', age = 20)

4、拆包

def myPrint(a, *args, **params):
    print(a)
    print(args)
    print(params)
    
args = (1, 2, 3);
params = {'name':'zs', 'age':20};
myPrint("zs", *args, **params)

打印结果：
zs
(1, 2, 3)
{'name': 'zs', 'age': 20}

5、匿名函数

def test(a, b, fn):
    return fn(a, b)
    
print(test(10, 20, lambda x,y:x+y))
print(test(10, 20, lambda x,y:x-y))
print(test(10, 20, lambda x,y:x*y))

def test(a, b, fn):
    return fn(a, b)

fn_new = input("请输入 lambda表达式：")
    
print(test(10, 20, eval(fn_new)))

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