Python_基础_Day_3

函数

一、定义函数

def my_abs(x):
    if x < 0:
        return -x
    else:
        return x

二、调用函数

my_abs(-10) # 10

三、参数

1、默认参数（默认参数必须指向不变对象）

def my_abs(x=2):
    if x < 0:
        return -x
    else:
        return x

2、可变参数(0个或任意个)

def calc(*numbers):
    sum = 0
    for n in numbers:
        sum += n*n
    return sum

print(calc(1,2,3,4)) # 30

l = [1,2,3,4]
#Python允许在list或tuple前面加一个*号，把list或tuple的元素变成可变参数传进
print(calc(*l))   # 30

3、关键词参数（0个或任意个包含参数名的参数，这些参数在函数内自动组成dict）,功能：扩展函数功能

def person(name, age, **kw):
    print('name:', name, 'age:', age, 'other:', kw)

person('char', 28)  # name: char age: 28 other: {}

person('char', 28, city='beijing') # name: char age: 28 other: {'city': 'beijing'}

person('char', 28, gender = 'M', job = 'Engineer') # name: char age: 28 other: {'gender': 'M', 'job': 'Engineer'}

extra = {'city': 'beijing', 'job': 'Engineer'}

person('char', 28, **extra) # name: char age: 28 other: {'city': 'beijing', 'job': 'Engineer'}

4、命名关键词参数（如果要限制关键字参数的名字，就可以用命名关键字参数，例如，只接收city和job作为关键字参数）

def person(name, age, *, city, job):
    print('name:', name, 'age:', age, city, job)

person('char', 28, city='beijing', job='Engineer') # name: char age: 28 beijing Engineer