【python入门到精通】python核心知识之参数与变量完全解读

def power(x, n):
return x ** n
print(power(2,2))

def power(x, n=2):
return x ** n
print(power(2))

def test(a=1, b=2, c=3):
print("a=%d b=%d c=%d" % (a, b, c))
test(c=2)

def test(L=[]):
   L.append("END")
print(L)
test([1, 1, 1])
test([2, 2, 2])

def test(L=[]):
L.append("END")
print(L)
test()
test()
输出结果：
['END']
['END', 'END']
函数在定义的时候，默认参数的值已确定，换句话说，L指向的地址是确定，之后如果还是对其内容进
行更改的话，默认参数的值也随之改变了
温馨提示：默认参数必须指向不可变对象

def sum(numbers):
total = 0
for i in numbers:
 total += i
return total
print(sum([1, 2, 3]))
y=[1,2,3]  换成（1,2,3）打印结果一样
for x in y:
    print(x)
输出：
6
1
2
3

def sum(*numbers):
total = 0
for i in numbers:
 total += i
return total
print(sum(1, 2, 3))
输出：
6

def my_fun(*numbers):
 print(type(numbers))
 total = 0
 for i in numbers:
  total += i
 return total
print(my_fun(1, 2, 3))
输出结果：
<class 'tuple'>
6

def person(name, age):
 print(name,age)
person("wiggin",29)

def person(name, age, *, pet):
 print(name,age,pet)
person("wiggin",29,pet="tomcat")

def person(name, age, *, pet):
 print(name,age,pet)
person("wiggin",29,"tomcat")
TypeError: person() takes 2 positional arguments but 3 were given

def person(name, age, *, pet="cat"):
print(name,age,pet)
person("wiggin",29)

关键字参数允许你传入0个或任意个含参数名的参数，这些关键字参数在函数内部自动组装为一个dict，**kw参数的作用如下
def person(name, age, **kw):
 print('name:', name, 'age:', age, 'other:', kw)
person("wiggin",29,city="广州",pet="cat")
输出：
name: wiggin age: 29 other: {'city': '广州', 'pet': 'cat'}

def person(name, age, **kw):
 print('name:', name, 'age:', age, 'other:', kw)
other_info = {"pet": "cat"}
person("wiggin",29,city="广州",**other_info)
输出：
name: wiggin age: 29 other: {'city': '广州', 'pet': 'cat'}