Collection Series Usage

deque bidirectional queue

Deque can add and remove elements from both ends. The common structure is its simplified version.

Deque supports the common operations of sequences, and now for a simple example, you will find that there is no difference between a flat list:

1 ImportCollections2 3Dic=collections.deque ('ABCDEFG')4 Print 'deque=', DiC5 Print 'Length:', Len (DIC)6 Print 'Left end:', Dic[0]7 Print 'Right end:', dic[-1]8Dic.remove ('C')9 Print 'Remove (c):'Dic

Direct mapping:

is not found with the list of the same, just become deque (list), the key is some basic usage is the same, a comparison chart it is more direct:

1listtest=['a','b','C','D','e','F','g']2 Print 'listtest=', Listtest3 Print 'Length:', Len (listtest)4 Print 'Left end:', Listtest[0]5 Print 'Right end:', listtest[-1]6Listtest.remove ('C')7 Print 'Remove (c):', Listtest

or Direct mapping:

Here's a unique place to go, two-way operation. Deque is the Extend method that initializes the collection element, and you can add the binding element from "left" to the collection by Extendleft:

1 ImportCollections2d1=Collections.deque ()3D1.extend ('ABCDEFG') #可以列表元素4 Print 'Extend:', D15D1.append ('h') #只会认为是一个元素加入6 Print 'Append:', D17 #Add to left8D2=Collections.deque ()9D2.extendleft (xrange (6)) #从左边加入元素Ten Print 'Extendleft:', D2 OneD2.appendleft (6) #从左边加入元素 A Print 'Appendleft:', D2

D1.append ('H') #只会认为是一个元素加入  

D1.extend ('abcdefg')  #可以列表元素  

Execution result diagram:

The pop and Popleft methods corresponding to the Append and Appendleft methods are used to remove elements from the collection, as shown in the following example:

1 Print " from the right"  2D1=collections.deque ('ABCDEFG')3 Print 'd1==', D14  whileTrue:5     Try:  6         PrintD1.pop (),7     exceptIndexerror:8          Break  9 Print  Ten Print '\ n from the left'   OneD2=collections.deque (xrange (6)) A Print 'd2==', D2 -  whileTrue: -     Try:   the         Printd2.popleft (), -     exceptIndexerror: -          Break   - Print                 

Execution Result:

Finally, it is worth mentioning that deque is thread-safe, meaning that you can operate from the left and right side of the Deque collection at the same time without affecting it, see the following code:

ImportCollectionsImportThreadingImportTime Candle=collections.deque (Xrange (5))  defBurn (direction,nextsource): whileTrue:Try: Next=Nextsource ()exceptIndexerror: Break          Else:              Print '%s:%s'%(Direction,next) time.sleep (0.1)      Print "Done %s"%directionreturn Left=threading. Thread (target=burn,args= (' Left', Candle.popleft)) Right=threading. Thread (target=burn,args= (' Right', Candle.pop)) Left.start () Right.start () Left.join () Right.join ( )

Collection Series Usage