Three artifacts-iterators, generators, and adorners

1. Iterators and generators 1.1 iteratorsBase iterator initialization and access

i = ITER (' abc ') print (i.__next__ ()) print (i.__next__ ()) print (
i.__next__ ()) for
I in ITER (' abc '):
    Print (i)

For a class, __iter__ (self) and __next__ (self) are required. Also, use the raise stopiteration to stop the iterator.

Class Myiterator (object):
    def __init__ (self):
        self.a = 0
        self.b = 1
    def __iter__ (self):
        return Self
    def __next__ (self):
        self.a,self.b = self.b,self.a+self.b
        if self.a>100000:
            raise Stopiteration # This will stop return automatically
        SELF.A for
N in Myiterator ():
    print (n)

1.2 GeneratorsBuilder: Yield. Access: obj.__next__ () 2. Closure of the packageNote Closure usage: Return internal function func is a function reference, func () is a function call

def greeting_conf (prefix):
    def greeting (name):
        print (prefix, name) return
    greeting mgreeting
= Greeting_conf ("Good Morning") # The mgreeting is now function:greeting
print ("Function name is:", mgreeting.__name__) 
print ("ID of mgreeting is:", ID (mgreeting))
print ()
agreeting = mgreeting ("Good Afternoon") 
print (" Inner function returns: ", agreeting)
print (ID of agreeting is:, ID (agreeting))

3. Decoration Device Class 3.1 methods: @classmethod and @staticmethodAvoid instantiating, you can call the method of the class directly.

Class MyClass:
    bar = 1
    def foo (self):
        print (' MyClass ')
    @classmethod #避免硬编码
    def classfoo (CLS):
        print (' Classfoo ', end= "")
        print (Cls.bar)
        cls (). Foo ()
        # Cls.foo () # This call will be an error. No self
    @staticmethod
    def staticfoo ():
        print (' Staticfoo ', end= "")
        print (Myclass.bar)
        MyClass (). Foo ()
        # Myclass.foo () # This call will be an error. No self
# no instantiation, direct call to
Myclass.classfoo ()
Myclass.staticfoo ()

3.2 @property class adorner@property equivalent to get, corresponding to the adorner, all need func+setter/deleter

Class MyClass:
    def __init__ (self):
        self.__x = None
    @property
    def x (self): return
        self.__x
    @ X.setter
    def x (self,value):
        self.__x = value
    @x.deleter
    def x (self):
        del self.__x

MyClass = MyClass ()
print (myclass.x) # calls @property
myclass.x = 100 # calls @x.deleter
print (myclass.x)
del ( myclass.x) # call @x.deleter
try:
    print (myclass.x)
except Exception as Error:
    print (' Fail ', error)

3.3 Custom adorners

Although there is a lot of understanding of the adorner, but the landlord still feel that the adorner is a function of the definition of behavior. (#^.^#) simplest adorner, closure + function parameters

def log (func):
    # most basic adorner
    def wrapper (*args,**kw):
        print ("Call%s ();"% func.__name__)
        # return Func (*args,**kw) # can not comment out, will call return
    wrapper
@log
def now ():
    print ("Now")

Adorner with parameters: 3-layer package, note that the declaration must have parentheses ...

def log (text= "I am Default text"):
    # Adorner with parameters
    def decorator (func):
        def wrapper (*args,**kw):
            print (func.__name_ _) Return
            func (*args,**kw) return
        wrapper return
    decorator
@log () #注意: When an adorner declaration has a parameter, the bracket def must
be Now ():
    print (' Now ') now
()

The following is a useful adorner usage that defines the function behavior.

def before (request, Kargs):
    print (' before ')
def after (request, Kargs):
    print (' after ')
def Filter ( Before_func, After_func):
    def outer (main_func):
        def wrapper (Request, Kargs):
            Before_result = Before_func (Request, Kargs)
            if (Before_result!= None): Return
                before_result
            main_result = main_func (Request, Kargs)
            if (Main_result!) = None): Return
                main_result
            after_result = after_func (Request, Kargs)
            if (After_result!= None):
                Return After_result return
        wrapper return
    outer
@Filter (before, after)
def Index (Request, Kargs) :
    print (' index ')
index (1,2)

Output results:

Before
index
after

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