函数

1.面向对象--》类

2.面向过程--》过程--》def

3.函数式编程--》def

 

#函数
def func1():
    '''this is a function'''
    print('in the func1')
    return 0
#过程（没有return)
def func2():
    '''this is a process'''
    print('in the func2')

x=func1()
y=func2()

print('the value of x is %s'%x)
print('the value of y is %s'%y)


结果：

in the func1
in the func2
the value of x is 0
the value of y is None

 

---

 

def test(x,y,z):
    print(x)
    print(y)
    print(z)

test(3,4,1)        #位置参数：与形参顺序一一对应
test(y=5,z=7,x=2)  #关键自参数：与形参顺序无关
test(3,z=5,y=7)      #位置参数一定要写在关键字参数的前面

test(4,5,z=8)

#默认参数特点:函数调用时，默认参数可传可不传
#作用：默认安装
def  conn(host,port=3306):
    pass

---

#接收的参数个数不固定
#*args：接收n个位置参数，转成一个tuple输出

def test(*args):
    print(args)

test(1,2,3,4,5,6)
test(*[1,2,3,4,5,6])
test('Alex')

(1, 2, 3, 4, 5, 6)
(1, 2, 3, 4, 5, 6)
('Alex',)

#一个固定参数，其余参数不固定
def test1(x,*args):
    print(x)
    print(args)

test1(1,2,3,4,5,6,7)

1
(2, 3, 4, 5, 6, 7)

#kwargs:把n个关键字参数，转换成字典的方式
def test2(**kwargs):
    print(kwargs)
    print(kwargs['name'])
    print(kwargs['age'])
    print(kwargs['sex'])

test2(name='alex',age=23,sex='F')
test2(**{'name':'alex','age':23,'sex':'f'})

{'name': 'alex', 'age': 23, 'sex': 'F'}
alex
23
F

def test3(name,**kwargs):
    print(name)
    print(kwargs)

test3('alex')

alex
{}

 

def test4(name,age=23,*args,**kwargs):
    print(name)
    print(age)
    print(args)      #args:位置参数
    print(kwargs)    #kwargs:关键字参数

test4('alex',3,23,36,sex='m',hobby='shopping')

alex
3
(23, 36)
{'sex': 'm', 'hobby': 'shopping'}

---

school='bupt'      #全局变量
def change_name(name):
    school='cnn of bupt'         #局部变量
    print("before change:",name,school)
    name='Alex'                  #局部变量
    print("after change:",name)

name='alex'
change_name(name)
print(name)
print('school:',school)

before change: alex cnn of bupt
after change: Alex
alex
school: bupt

局部变量不能使全局变量的值发生改变的情况：1.字符串 2.单独的整数

而定义为全局变量的列表和字典，可以通过局部变量更改它们的值。

name=['alex','xuhang','mengmeng']

def change_name(name):
    name[0]='ALEX'
    print('in the function',name)

change_name(name)
print(name)

in the function ['ALEX', 'xuhang', 'mengmeng']
['ALEX', 'xuhang', 'mengmeng']