生成器、装饰器、迭代器

>>> l = [i*2 for i in range(10)]  #直接生成列表，会把数据全部加载
>>> l
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
>>> g = (i*2 for i in range(10)) #生成一个生成器则会返回个内存地址，然后可以通过next方法一个一个的取值，如果很多后面的值不需要使用，我们就可以节约很多内存
>>> g
<generator object <genexpr> at 0x0000010E2E6A5DB0>
>>> next(g)
0
>>> next(g)
2
>>> next(g)
4
>>> next(g)
6
>>> next(g)
8
>>> next(g)
10
>>> next(g)
12
>>> next(g)
14
>>> next(g)
16
>>> next(g)
18
>>> next(g)  #每次调用next方法，就会计算出下一个元素的值，直到计算出最后一个就会跑出StopIteration的异常
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
StopIteration

>>> g = (x **2 for x in range(5))
>>> g
<generator object <genexpr> at 0x0000010E2E6A5570>
>>> for i in g:
...  print(i)
...
0
1
4
9
16

>>> def fib(n):
...  i,a,b = 0,0,1
...  while i<n:
...   print(b)
...   a,b = b,a+b
...   i += 1
...  return "done"
...
>>> fib(5)
1
1
2
3
5

>>> def fib(n):
...  i,a,b = 0,0,1
...  while i<n:
...    #print(b)
      yield b   #修改成yield  b即可
...   a,b = b,a+b
...   i += 1
...  return "done"
...
>>> fib(5)
<generator object fib at 0x0000010E2E6A5D00

def fib(n):
    i, a, b = 0, 0, 1
    while(i<n):
        yield b
        a, b = b, a+b
        i += 1
    return 'done'

data = fib(5)
print(data)
print(data.__next__())
print(data.__next__())
print("我来打断一下")
print(data.__next__())

#结果如下
<generator object fib at 0x000002766915D6D0>
1
1
我来打断一下
2

data = fib(5)
while True:
    try:
        x = next(data)
        print("data=",x)
    except StopIteration as e:
        print("generator return value:",e.value)
        break

#程序结果是
data= 1
data= 1
data= 2
data= 3
data= 5
generator return value: done #这样我们就可以获取到这个返回值

def func(x, y, f):
    print(f(x)+f(y))

func(-3,9,abs)

#执行结果
12

def func(x):
    def func1(y):
        print(y)
    func1(x)

func(4)
#执行结果是
4

import time
def bar(): #原函数，也就是要被装饰的函数
    time.sleep(1)
    print('in the bar')

def test(f):
    start_time=time.time()
    f()
    stop_time=time.time()
    print("the f run time is %s" %(stop_time-start_time))

bar()
print("分割线".center(50,'-'))
test(bar)

#程序结果如下
in the bar
-----------------------分割线------------------------
in the bar
the f run time is 1.0021047592163086

Process finished with exit code 0

import time
#其实就是利用嵌套函数+高阶函数连用
def timer(func): #timer(test1)  func=test1
    def deco(*args,**kwargs): #通过可变参数解决相对应的原函数传来的参数问题，这样就很灵活
        start_time=time.time()
        func(*args,**kwargs)   #run test1()
        stop_time = time.time()
        print("the func run time  is %s" %(stop_time-start_time))
    return deco  
@timer  #这个相当于test1=timer(test1)
def test1():
    time.sleep(1)
    print('in the test1')

@timer # test2 = timer(test2)  = deco  test2(name) =deco(name)
def test2(name,age):
    print("test2:",name,age)

test1()
test2("HZhuizai",22)
#程序执行结果如下
in the test1
the func run time  is 1.0001072883605957
test2: HZhuizai 22
the func run time  is 0.0

import time
user,passwd = 'alex','abc123'
def auth(auth_type):
    def outer_wrapper(func):
        def wrapper(*args, **kwargs):
            print("wrapper func args:", *args, **kwargs)
            func()
            if auth_type == "local":
                print("local 模式验证")
            elif auth_type == "ldap":
                print("ldap 模式验证")
        return wrapper
    return outer_wrapper

@auth(auth_type="local") # home = wrapper()
def home():
    print("welcome to home  page")
    return "from home"

@auth(auth_type="ldap")
def bbs():
    print("welcome to bbs  page")

home() #wrapper()
print("分隔符".center(50,'-'))
bbs()

#程序执行结果
wrapper func args:
welcome to home  page
local 模式验证
-----------------------分隔符------------------------
wrapper func args:
welcome to bbs  page
ldap 模式验证

>>> from collections import Iterable
>>> isinstance([],Iterable)
True
>>> isinstance("",Iterable)
True

>>> from collections import Iterator
>>> isinstance((x for x in range(10)), Iterator)
True
>>> isinstance([x for x in range(10)], Iterator)
False

>>> isinstance(iter([]), Iterator)
True
>>> isinstance(iter('abc'), Iterator)
True