Python function three (adorner)

One. function names (scientific name: First Class object)

The function name is essentially the memory address of the function. Popular point is a special ordinary variable

def func ():     Print (111) func () Print (func) # Results: # 111 # <function func at 0x00000150713f6048>

1. Can be referenced (that is, can be assigned to other variables)

def func ():     Print (' infunc'= FUNCF ()#  Result:# in func 

2. Elements that can be used as container types

def func ():     Print (111) def Func2 ():     Print (222) def func3 ():     Print (333= [Func (), Func2 (), func3 ()] for in li:    i#  Results: 111      222      333

3. Can be used as a function parameter and return value

def func ():     Print (111) func () def Func2 ():     return  = Func2 () f ()#  Result:         run from top to bottom, call function after meeting func () to print a 111,#             after 111 to F = Func2 (), call Func2 () to return to f a value of Func,#  111            last F () that is func () once again called after printing a 111

The first class of objects (first-class object) refers to

1. Can be created at run time

2. Can be used as function parameter or return value

3. Entities that can be stored in variables.

Two. Closed Package

Closure definition: An inner layer function, a reference to a variable of the outer layer function (non-global), called a closure

Use of closures: If your memory function is a closure, there is a mechanism inside python that encounters closures

He will open a memory space in memory and will not close with the end of the function

 fromUrllib.requestImportUrlopenPrint(Urlopen ('http://www.cnblogs.com/jin-xin/articles/8259929.html'). Read ())defindex (URL): Content=urlopen (URL). Read ()defget (): With open ('crawler','a') as F1:f1.write (Content.decode ('Utf-8'))    returnGetIndex ('http://www.cnblogs.com/jin-xin/articles/8259929.html') () index ('http://www.cnblogs.com/jin-xin/articles/8259929.html') () index ('http://www.cnblogs.com/jin-xin/articles/8259929.html') () index ('http://www.cnblogs.com/jin-xin/articles/8259929.html') () index ('http://www.cnblogs.com/jin-xin/articles/8259929.html')()defindex (): URL="http://www.xiaohua100.cn/index.html"    defget ():returnurlopen (URL). Read ()returnGet

crawling Web pages (closures)

Determine if it is a closure function: __closure__

EF func (): Name='Alex'    defFunc2 ():Print(name) Func2 ()Print(Func2.__closure__)#contains the cell is the closure None is not a closurefunc ()#Results:#Alex#(<cell at 0x0000011ad42a75b8:function object at 0x0000011ad6178a60>, <cell at 0x0000011ad42a75e8:str objec T at 0x0000011ad6177378>)name='Alex'deffunc ():defFunc2 ():Print(name) Func2 ()Print(Func2.__closure__)#None is not closuresfunc ()#Results:#Alex#Nonedeffunc (x):defFunc2 ():Print(x) Func2 ()Print(Func2.__closure__) func ('Alex')#Results:#Alex#(<cell at 0x0000029d98ce75b8:str object at 0x0000029d98d77538>)

Three. Perform intrinsic functions inside an outer function

def func ():     def Func2 ():         Print (111)    Func2 () func()def  func ():    def  Func2 ():         Print (111)     return Func2func () ()

Four. Decorative Device

For example, calculating the execution efficiency of a function

1. The simplest notation

Import Timedeffunc ():Print('We're all the same .') Start_time=time.time () time.sleep (0.1) func () End_time=time.time ()Print('execution efficiency of------%s'% (end_time-start_time))#Results:#We're all the same .#------Execution Efficiency 0.10034990310668945

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2. Advanced wording

 import   time  def   func ():  print  ( "  We're all the same  "  )  def   Timmer (): start_time  = Time.time () time.sleep ( 0.1 Time.time ()  prin T  ( " ------execution efficiency%s  " % (End_time-start_time)) Timmer ()  #   Although it can also run, it affects the normal operation of Func () and can also be advanced  

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3. Simple Decorative Device

Import Timedeffunc ():Print('We're all the same .')defTimmer (f):definner (): Start_time=time.time () time.sleep (0.1) F () End_time=time.time ()Print('execution efficiency of------%s'% (end_time-start_time)) returnInnerfunc=Timmer (func) func ()#can be understood as func,timmer,inner through assignment conversion, adding parameters, and finally only one func,#This allows you to run the program and to know the execution efficiency

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4. Adorner with return value (Syntax sugar usage)

@timmer equivalent to #func = Timmer (func) is the name of the function to be asked for (the name of the letter to be asked)

Import TimedefTimmer (func):defInner (*args,**kwargs): Start_time=time.time () time.sleep (0.1) ret=func (*args,**kwargs) end_time=time.time ()Print('------Execution Efficiency%s'% (end_time-start_time)) returnretreturnInner@timmerdeffunc ():return 'If the sky is also old, the human path is vicissitudes'#func () cannot write this step if it prints the return value, otherwise the function will be called once, and the execution efficiency can be printed once more Print(func ())#Results:#------Execution Efficiency 0.1002659797668457#If the sky is also old, the human path is vicissitudes

5. General Purpose Decorators

def Wrapper (func):     def Inner (*args,**Kwargs):        "         action before executing function "' = func ( *args,**Kwargs)        ' operation after executing function ''        return  ret     return Inner@wrapper def func ():     Print (111) func ()

Python function three (adorner)