Python full stack development: Python function advanced

Python function nested Function object namespace and scope closure function adorner one, function nesting

Nested Definitions of functions

def func1 ():     Print ('fromfunc1')     def # func2= memory address        Print ('fromfunc2')     Print (FUNC2) func1 ()

Nested calls to functions

#Compare the size of a two numberdefmax2 (x, y):ifX >y:returnxElse:        returny#Compare the size of a three numberdefmax3 (x, Y, z): Res1=max2 (x, y) res2=max2 (res1,z)returnRes2Print(Max3 (11,199,2))

# Results
# 199

Second, the Function object

function is the first class of objects in Python

1. Can be referenced

X=1y=xdef  Bar ():    print('frombar'  F=bar   #  The value that bar represents when assigned as an object is the memory address F ()

2. Parameters can be passed in (the nature of the function name, memory address of functions)

F=func

3. The return value of the function can be

def Bar (x):     Print (x)    x () bar (func)

4. Elements of the container type can be

def # X=func    return # return func Res # Res=func # Print (res)res ()    

Namespaces and scope namespaces: space to hold names and binding relationships

Namespaces fall into three categories

Built-in namespaces: holds the Python interpreter's own name, takes effect when the interpreter starts, and fails when the interpreter is closed

Global namespace: A file-level name that takes effect when the file is executed and is invalidated when the file ends or is deleted during file execution

Local namespaces: The names defined in the stored functions (parameters of functions and names within functions are stored and local namespaces), #在函数调用时临时生效, function ends are invalidated

Load order and order of values between three namespaces:
Load order: Built-in (load on interpreter startup, load before program runs)--global (loaded from top to bottom)--local (loaded at call time)---> Built-in

Value: In local call: Local namespace---> global namespace---> Built-in namespaces

To look at the global scope:

Global----Built-in----local use:

the global cannot use local

The local can use the global

Scope : Is the range of action

1, namespaces and scopes are inseparable.

2, the scope is divided into two kinds

Global scope: The global namespace and the name of the built-in namespace are globally scoped and can be referenced anywhere in the entire file, effectively globally

Local scope: Local namespace, only valid locally

3, stand in the global view

When using a name, if it is global, use the global

If the global is not, use the built-in

4, why should have scope

For variables within a function do not affect the global

5.

Pass

Four, closed packet function

Closures: 1. Closed: Internal function
2. Package: Contains a reference to a variable in the scope of an external function

def Hei (): x=20 def  Inner ():x# if x is defined, he will use his own, it will not implement the closure print

#def  Hei (): x=20 def  Inner ():  " ' closure function "printreturn  inner () the common form of the closure function 　　　　

Method of judging closure function: __closure__

#the __closure__ of the output has a cell element: a closure functiondeffunc (): Name='Eva'    definner ():Print(name)Print(Inner.__closure__)    returnInnerf=func () f ()#the output __closure__ is none: Not a closure functionName ='Egon'defFunc2 ():definner ():Print(name)Print(Inner.__closure__)    returnInnerf2=Func2 () f2 ( )

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Closed Packet Acquisition Network application

# From urllib.request import Urlopen # def index (URL): #      def inner ():#         return  urlopen (URL). Read ()#     return Inner#  u= ' Http://www.cnblogs.com/Eva-J/articles/7156261.html#_label1 '# get = Index (u) # print (Get ())

View CodeFive, decorative device

Pass

Python full stack development: Python function advanced