Python函数参数分类使用与新特性详细分析讲解

def print_num(num):
    print(num)
a = 10
print_num(a)  # 实参引用传递給 形参 num

def locationParams(m,n):
    print('第一个参数',m)
    print('第一个参数',n)
locationParams(1,2)

def defaultParams(m,n='xiaoming'):
    print('第一个参数',m)
    print('第一个参数',n)
defaultParams('Hello','xiaoli')
defaultParams('Hello') #未传入默认参数
"""
第一个参数 Hello
第二个参数 xiaoli
第一个参数 Hello
第二个参数 xiaoming
"""

def defaultParams(m='xiaoming',n):
    print('第一个参数',m)
    print('第二个参数',n)
defaultParams('Hello')  #Python 按照顺序传参，那么没有实参会传递给形参n

def f(a,l=[]):
    l.append(a)
    return l
print(f(1))
print(f(2))
print(f(3))   
## 默认参数l为list，其对应的值也被修改了
"""
[1]
[1, 2]
[1, 2, 3]
"""

def variableParams(*params):
    print("参数: ",params)
    sum = 0
    for i in params:
        sum+=i
    print(sum)
variableParams()  # 不传入参数
variableParams(1,2,3,4)  # 传入多个参数
num_list = [1,2,3,4]
variableParams(*num_list) # num_list 加上“*” 将num_list拆解，否则num_list被当成一个参数传入
variableParams(num_list[0],num_list[1]) 

def keyWordParams(**params):
    print(params)
keyWordParams()  ## 不传参数
keyWordParams(name='xiaoming',age='11',gender='male')  ## 关键字传参
person_info = {'name': 'xiapli', 'age': '20', 'gender': 'male'}
keyWordParams(**person_info)  # **person_info 将字典拆分
"""
{}
{'name': 'xiaoming', 'age': '11', 'gender': 'male'}
{'name': 'xiapli', 'age': '20', 'gender': 'male'}
"""

def pos_only(a,/):
    print(a)
pos_only(1)  # 1
pos_only(a=1)  
# TypeError: pos_only() got some positional-only arguments passed as keyword arguments: 'a'

def stu_info(name,gender,*,age,city):
    print('name is:',name,' gender is:',gender,' age:',age,' city:',city)
stu_info('Bob','M',age=7,city='TJ')
stu_info('Lucy','F',city='BJ',age=10)

stu_info('Lucy','F',city='BJ',addr=10)
# stu_info() got an unexpected keyword argument 'addr'

#args可以传递一个tuple 其后只能传递age和city参数
def stu_info(name,gender,*args,age,city):
    print('name is:',name,' gender is:',gender,' age:',age,' city:',city)
    for i in args:
        print('args:',i)
stu_info('Bob','M',age=7,city='TJ')
stu_info('Lucy','F',(2,3),city='BJ',age=10)
"""
name is: Bob  gender is: M  age: 7  city: TJ
name is: Lucy  gender is: F  age: 10  city: BJ
args: (2, 3)
"""

def function1(a, b, c=0, *arg, **kw):
    print('a =', a, 'b =', b, 'c =', c, 'arg=',arg, 'kw =', kw)
function1(1,2,3,4,5,A=1,B=2)
# a = 1 b = 2 c = 3 arg= (4, 5) kw = {'A': 1, 'B': 2}
def function2(a,/, b, c=0, *arg, **kw):
    print('a =', a, 'b =', b, 'c =', c, 'arg=',arg, 'kw =', kw)
function2(1,2,3,4,5,A=1,B=2)
# a = 1 b = 2 c = 3 arg= (4, 5) kw = {'A': 1, 'B': 2}
def function3(a, b, c=0, *, d, **kw):
    print('a =', a, 'b =', b, 'c =', c, 'd =', d, 'kw =', kw)  
function3(1,2,3,d=4,A=1,B=2)
# a = 1 b = 2 c = 3 d = 4 kw = {'A': 1, 'B': 2}
def function4(a, b, c=0, *arg, d, **kw):
    print('a =', a, 'b =', b, 'c =', c, 'arg=',arg, 'd =', d, 'kw =', kw)
function4(1,2,3,4,5,d=6,A=1,B=2)
# a = 1 b = 2 c = 3 arg= (4, 5) d = 6 kw = {'A': 1, 'B': 2}