Python Development function Advanced: An iterative & iterator & Generator

One, an iterative & iterative object

1. The value of one is an iterative iterable
#str List Tuple Set Dict
#可迭代的--The corresponding Mark __iter__

2. Determine if a variable is not an iterative

# print (' __iter__ ' in Dir (list))
# print (' __iter__ ' in dir ([+)])

3. Iterative protocol--there is a __iter__ method in the interior of any iteration

Second, iterators

1. Converting an iterative to an iterator

1 #!/usr/bin/env python2 #_*_coding:utf-8_*_3 4 #iterator #迭代器5 #iterator iterable# iterative objects6L = [1,2,3,4,5]7  forIinchL:8     Print(i)9 Print(ITER (L))#built-in function iter = = L._iter_ ()TenL.__iter__() OneL_iterator =iter (L) A Print(Set (dir (l_iterator))-Set (dir (l))) - Print(Next (L_iterator))#The iterator is going to use the next method to take the value

2. Iterator Summary

#迭代器里既有iter方法, and next method--iterator protocol
The result of #通过iter (O) is an iterator,
#o是一个可迭代的

#迭代器 are mostly used inside python, and we'll just use them.
#迭代器: Built-in __iter__ and __next__ methods

1 #!/usr/bin/env python2 #_*_coding:utf-8_*_3 4L = [1,2,3,4,5]5L_iterator =iter (L)6 Print(L_iterator.__next__())7 Print(L_iterator.__next__())8 Print(L_iterator.__next__())9 Print(L_iterator.__next__())Ten Print(L_iterator.__next__()) OneNext (L_iterator)#==l_iterator.__next__ () A #While True: Write your own equivalent for loop - #Try: - #print (Next (l_iterator)) the #except stopiteration: - # Break

3. An easy way to determine whether it is an iterator or an iterative object

1 #!/usr/bin/env python2 #_*_coding:utf-8_*_3 4  fromCollectionsImportiterable5  fromCollectionsImportIterator6 #s = ' abc '7 #Print (Isinstance (s,iterable)) s is not an iterative object8 #Print (Isinstance (s,iterator)) s is not an iterative object9 #Print (Isinstance (ITER (s), Iterator))

4. Iterators and iterators

#不管是一个迭代器还是一个可迭代对象, you can use the For loop to traverse
#迭代器出现的原因 Save Memory for you

Third, generator

#生成器函数
#生成器的本质就是迭代器

1 #!/usr/bin/env python2 #_*_coding:utf-8_*_3 4 deffunc ():5     Print('AAAA')6A = 17     yieldA#returns the first value8     Print('bbbb')9     yield12#returns a second valueTen #error value, equivalent to three new generators One #G1 = func () A #g2 = func () - #g3 = func () - #Print (Next (func))) #取第一个值 the #Print (Next (func))) #取第二个值 - #Print (Next (func))) #取第三个值 will error because there is no third value - #The correct value is the same generator - #ret = func () #拿到一个生成器 + ## Print (ret) - #print (Next (ret)) #取第一个值 + #print (Next (ret)) #取第二个值 A #print (ret) #取第三个值 An error because there is no third value

3,1 Generator Make clothes instance

1 #/usr/bin/env python2 #_*_coding:utf-8_*_3 4 defMake_cloth ():5      forIinchRange (2000000):6         yield "Item %s Dress"%I7 #szq = Make_cloth ()8 #print (Next (SZQ))9 #print (Next (SZQ))Ten # One #print (Next (SZQ)) A #For i in range: - #print (Next (SZQ))

3.2 Listening to a file instance

1 #!/usr/bin/env python2 #_*_codinglutf-8_*_3 4 #Listening file tail-f5 Import Time6 deftail (filename):7 With open (filename) as F:8F.seek (0, 2)#count from the end of the file9          whileTrue:Tenline = F.readline ()#read new lines of text in a file One             if  notLine : ATime.sleep (0.1) -                 Continue -             yield Line the  - #For line in tail (' Tmp_file '): - #print (line,end = ")

3.3 Calculating the moving average

1 #!/usr/bin/env python2 #_*_coding:utf-8_*_3 4 #average annual income for the year of 7th5 defAverager ():6Total =07Day =08Avrage =09      whileTrue:TenDay_num =yieldAvrage#return Avrage OneTotal + =Day_num ADay + = 1 -Avrage = total/ Day -  the #avg = Averager () - #num = Next (avg) #激活生成器 avg.send (), nothing like send and next effect - #print (avg.send) #传值 next - #print (Avg.send )

3.4 Builder with Adorner

1 #!/usr/bin/env python2 #_*_codinglutf-8_*_3 4 defWrap (func):5     defInner (*args,**Kwargs):6g = func (*args,**Kwargs)7 Next (g)8         returng9     returnInnerTen  One @wrap A defAverager (): -Total =0 -Day =0 theAvrage =0 -      whileTrue: -Day_num =yieldAvrage#return Avrage -Total + =Day_num +Day + = 1 -Avrage = total/ Day +  A #g = Averager () at #Print (G.send (ten)) - #print (G.send )

Python Development function Advanced: An iterative & iterator & Generator