2018.8.10 iterators in Python

Main content:

1. Use of function names

2. Closed Package

3. iterators

Application of Function name

The function name is a variable, but he is a special variable, with parentheses to match the variables of the executable function.

1. memory address of Function name

def func ():     Print (' hehe ') Print (func) # Results # <function func at 0x000000000215d7b8>

2. Function name can be assigned to other variables

def func ():     Print (' hehe ') Print  = Funca ()

3, function name can be used as the element of the container class

 deffunc1 ():Print("I was 1 .") defFunc2 ():Print("I was 2 .") deffunc3 ():Print("I was 3 .") LST=[Func1, Func2, func3] forElinchLst:el ()

4. Function name can be used as parameter of function

 def   func ():  print  ( "  Did you eat  "  )  def   Func2 (FN):  print  ( '   I am func2  "  ) FN ()  print  ( "  I'm Func2   " ) Func2 (func)   

   5, function name can be the return value of a function

def   Func_1 ():  print  ( "  here is the function 1  "  )  def   func_ 2 ():  print  ( '   Here is the function 2  "  )  print  ("   here is the function 1  Span style= "COLOR: #800000" > " )  return   FUNC_2FN  = Func_1 () FN ()  

Second, closed package

A closure is a reference to an inner layer function (non-global) variable of the outer layer function. You can use __CLOSURE__ to detect whether a function is closed, return a cell is a closure, and return none is not a closure.

def func1 ():     ' Alex '    def Func2 ():         Print (name)    Func2 ()    print(func2.  __closure__) func1 ()

Call an intrinsic function outside the function:

If you have multiple layers of nesting, you need to go back one layer at a level:

Benefits of closures:

1. Protect your variables from external influences

2, can let the variable resident memory

Three, iterators

To see whether an object can iterate methods:

Wild path:

L = [1,2,3,4= L.__iter__()print('__iter__'in  dir (it))print('__next__' in Dir (it))

Official method:

Use the while loop + iterator to simulate A for loop:

LST = ['haha','hehe','La la','Ho Ho']it= LST.__iter__() while1:    Try: El= it.__next__()        Print(EL)exceptstopiteration: Break

Summarize:

Iterable: An iterative object containing the __iter__ () function inside

Iterator: Iterator with internal __iter__ () containing __next__ ().

Features of iterators:

1. Save Memory

2. Inertia mechanism

3, can not be repeated, only down execution

2018.8.10 iterators in Python