Python Enumerate Usage Summary __python

Enumerate () description Enumerate () is a Python built-in function enumerate the dictionary is enumerated, enumerated meaning for an iterative (iterable)/Ergodic object (such as lists, strings), enumerate it into an index sequence, It allows both index and value enumerate to be used for counting in the For loop

For example, for a seq, get:

(0, Seq[0]), (1, seq[1]), (2, seq[2])
      
      
       
       1
      
      

Enumerate () Returns a enumerate object, for example:
enumerate () using If you have a list that traverses both the index and the elements, you can first write this:

List1 = ["This", "yes", "one", "test"] for
I in range (len (list1)):
    print I, List1[i]
    
    
     
     1
     
     2
     
     3
    
    

The above method is somewhat cumbersome, using enumerate () will be more direct and graceful:

List1 = ["This", "yes", "one", "test"] for
index, item in enumerate (LIST1):
    print Index, item
>>>
0 This 
   1 is
21
3 Test
    
    
     
     1
     
     2
     
     3
     
     4 5 6 7 8
    
    

Enumerate can also receive a second parameter that specifies the starting value of the index, such as:

List1 = ["This", "yes", "one", "test"] for
index, item in enumerate (List1, 1):
    print Index, item
>>>
1
of this 2 is
31
4 test
    
    
     
     1
     
     2 3 4 5 6 7 8
    
    

Supplements

If you want to count the number of rows in a file, you can write this:

count = Len (open (filepath, ' R '). ReadLines ()) 1 

This method is simple, but may be slow, and cannot even work when the file is larger .

Can take advantage of enumerate ():

count = 0 for index, line in enumerate (open (filepath, ' R ')): Coun t = 1 1 2 3 

Reprint: http://blog.csdn.net/churximi/artic le/details/51648388