Superposition decorator:

In the same object to be decorated, add multiple decorators, and performs

@ Decoration 1

@ Decoration 2

@ Decoration 3

def decorated objects ():

pass

Note: decorator calling function is decorative objects will be added

Superposition decorator:

- the order of the decorator: from the bottom to top

- The order of execution: from the bottom to top

Note: Regardless of any judgment appeared in the inner, the last to be returned "after the call is decorative objects" func (* args, ** kwargs)

There are parameters decorator:

Essentially no reference in the decorative outer sheath of a function

No reference decorator can refer to the outer function's name

application:

    用户权限的认证

Iterator

Iterator:

The value of the iteration tools

Iteration:

Refers to iteratively repeated iterations, each iteration is based on a result of generating

Iterator:

Iterator refers to the value of the iterative tool that can be iterated values

If you want to know what python iterator is, you first need to know what is iterables?

Iterables:

All sequence types: str (string), list (list), tuple (ancestral), dict (dictionary), set (collection), f (file)

Any internal __ iter__ () method is iterable

Iterables:

By iterables __ iter __ (), the obtained return value "iterator object"

Iteration is the iteration value of the tool, it is to value iteration

Gets an iterator:

list1 = [1,2,3]

#调用__iter _ ()会得到一个返回值，该返回值就是一个迭代器对象

iter_list = list1._iter ()

--- How iteration values:

Iterator object __ next__ () Each time, will remove a value from the iterator object

Note: Take the last value, if the value is not, the error

while True
    try:
        print(iter_list._next_())
    except StopIteration:
        break

for loop principle:

in: iterables will automatically call _ iter _ () becomes the iterator object

for i in iterables:

# Will automatically help you call _ next_

print (i): for the inner loop will have a mechanism to catch the exception, in the event of abnormal values will stop

Iterator advantages and disadvantages:

Advantages: to provide a value of the index is not dependent manner

Save memory space

Disadvantages: the value specified in trouble, each value should start from the first look

Can not be calculated length len