函数的传参
让一个函数接受任意数量的位置参数，可以使用一个 * 参数
1 def avg(first , *rest): 2 3 return (first + sum(rest)) / (1 + len(rest)) 4 5 print(avg(1,2,3))
为了接受任意数量的关键字参数，使用一个以 ** 开头的参数
1 import html 2 3 def make_element(name , value , **attrs): 4 5 keyvals = [' %s="%s"' % item for item in attrs.items()] 6 7 attr_str = ''.join(keyvals) 8 9 element = '<{name}{attrs}>{value} </{name}>'.format(name=name , attrs=attr_str , value=html.escape(value)) 10 11 return element 12 13 14 15 str = make_element('item' , 'Albatross' , size="large" , quantity=6) 16 17 p = make_element('p' , '<spam>')
只接受关键字参数的函数
1 def mininum(*values , clip=None): 2 3 m = min(values) 4 5 if clip is not None: 6 7 m = clip if clip > m else m 8 9 return m 10 11 12 13 minnum = mininum(1,23,43,4,34,3,4, clip=3) 14 15 print(minnum) 16 17
函数参数注解
1 >>> def add(x:int , y:int)->int: 2 3 ... return x+y 4 5 ... 6 7 >>> str = add(2,3) 8 9 >>> str 10 11 5 12 13 >>> help(add) 14 15 Help on function add in module __main__: 16 17 18 19 add(x:int, y:int) -> int 20 21 22 23 >>> add.__annotations__ 24 25 {'y': <class 'int'>, 'return': <class 'int'>, 'x': <class 'int'>}
匿名或内联函数
1 lambda 2 3 >>> add = lambda x, y: x + y 4 5 >>> add(2,3) 6 7 5
lambad 遇到自由变量时
1 >>> x =10 2 3 >>> a = lambda y : x +y 4 5 >>> x = 20 6 7 >>> b = lambda y:x+ y 8 9 >>> a(10) 10 11 30 12 13 >>> b(10) 14 15 30 16 17 >>>
如果你想让某个匿名函数在定义时就捕获到值，可以将那个参数值定义成默认参数
即可，就像下面这样：
1 >>> x = 10 2 3 >>> a = lambda y, x=x: x + y 4 5 >>> x = 20 6 7 >>> b = lambda y, x=x: x + y 8 9 >>> a(10) 10 11 20 12 13 >>> b(10) 14 15 30 16 17 18 19 partial()
函数允许你给一个或多个参数设置固定的值，减少接下来被调用时的参数个数
1 def spam(a, b, c, d): 2 3 print(a, b, c, d) 4 5 6 7 >>> from functools import partial 8 9 >>> s1 = partial(spam, 1) # a = 1 10 11 >>> s1(2, 3, 4) 12 13 1 2 3 4 14 15 >>> s1(4, 5, 6) 16 17 1 4 5 6 18 19 >>> s2 = partial(spam, d=42) # d = 42 20 21 >>> s2(1, 2, 3) 22 23 1 2 3 42 24 25 >>> s2(4, 5, 5) 26 27 4 5 5 42 28 29 >>> s3 = partial(spam, 1, 2, d=42) # a = 1, b = 2, d = 42 30 31 >>> s3(3) 32 33 1 2 3 42 34 35 >>> s3(4) 36 37 1 2 4 42
回调函数的使用
1 def apply_async(func, args, *, callback): 2 3 result = func(*args) 4 5 callback(result) 6 7 8 9 >>> def print_result(result): 10 11 ... print('Got:', result) 12 13 14 15 >>> def add(x, y): 16 17 ... return x + y 18 19 20 21 >>> apply_async(add, (2, 3), callback=print_result) 22 23 Got: 5 24 25 >>> apply_async(add, ('hello', 'world'), callback=print_result) 26 27 Got: helloworld
闭包函数
1 #闭包函数 2 3 def sample(): 4 5 n = 0 6 7 def func(): 8 9 print('n=' , n) 10 11 12 13 def get_n(): 14 15 return n 16 17 18 19 def set_n(value): 20 21 nonlocal n 22 23 n =value 24 25 26 27 func.get_n = get_n 28 29 func.set_n = set_n 30 31 return func 32 33 34 35 f = sample() 36 37 f.set_n(1999) 38 39 print(f.get_n())
nonlocal 声明可以让我们编写函数来修改内部变量的值
-- dmo --
1 import sys 2 3 class ClosureInstance: 4 5 def __init__(self , locals=None): 6 7 if locals is None: 8 9 locals = sys._getframe(1).f_locals 13 self.__dict__.update((key ,value) for key , value in locals.items() if callable(value)) 14 16 17 def __len__(self): 18 19 return self.__dict__['__len__']() 20 21 22 23 def Stack(): 24 25 items = [] 26 27 def push(item): 28 29 items.append(item) 30 31 32 33 def pop(): 34 35 return items.pop() 36 37 38 39 def __len__(): 40 41 return len(items) 42 43 44 45 return ClosureInstance() 46 47 48 49 50 51 s = Stack() 52 53 s.push(10) 54 55 print(s.pop())
