python-2函数

Posted 2020-11-03 深圳丶追

http://docs.python.org/3/library/functions.html 或者菜鸟中文资料

1-使用函数

abs(-20)#求绝对值
max(1,4,200,3,2) #求最大的值
int(12.34) #转成int
float("12.34") #转成float
str(1.23) #转成字符串
bool(1) #转成bool类型
bool(‘‘) 

 2-自定义函数

def my_abs(x):
    if not isinstance(x, (int, float)):
        return 222
    if x >= 0:
        return x
    else:
        return -x

  x,y=(111,222);  x值是111,y值是222. 函数可直接返回tuple函数

3-函数的参数

　　3.1 默认参数， 定义默认参数要牢记一点：默认参数必须指向不变对象！

def sum(x, n=2): 
    return x+n
sum(5)#相当于调用power(5, 2)：

def enroll(name, gender, age=6, city=‘Beijing‘):
    print(‘city:‘, city)
enroll(‘Adam‘, ‘M‘, city=‘Tianjin‘) #可以只传指定参数

   

3.2 可变参数

def calc(*numbers): #*表示可变
    sum = 0
    for n in numbers:
        sum = sum + n * n
    return sum
calc(1,2,3) #参数调用

nums=[1,2,3]
calc(*nums) #第二种方式

 3.3 关键字参数

def person(name, age, **kw):
    print(‘name:‘, name, ‘age:‘, age, ‘other:‘, kw)
    
extra = {‘city‘: ‘Beijing‘, ‘job‘: ‘Engineer‘}
person(‘Jack‘, 24, **extra)

 3.4命名关键字参数

def person(name, age, *args, city=‘beijing‘, job):
    print(name, age, args, city, job)
person(‘xiaofeng‘,12,city=‘shenzhin‘,job=‘myjob‘)    
    
extra = {‘city‘: ‘Beijing‘, ‘job‘: ‘Engineer‘}
person(‘xiaofeng‘,12,**extra)

 

3.5参数组合

def f1(a, b, c=0, *args, **kw):
    print(‘a =‘, a, ‘b =‘, b, ‘c =‘, c, ‘args =‘, args, ‘kw =‘, kw)
    
args = (1, 2, 3, 4)
kw = {‘d‘: 99, ‘x‘: ‘#‘}
f1(*args, **kw) #a = 1 b = 2 c = 3 args = (4,) kw = {‘d‘: 99, ‘x‘: ‘#‘}