How to get index (array subscript) in loop

How to get the index value of the list?

ints = [8, 23, 45, 12, 78]

If you can add a state variable like C or PHP, the best choice for using Python here is to use Build the function enumerate

for i in range (0,len(list)):
      print i ,list[i]

But this method is a bit cumbersome. Using the built-in enumerrate function will be more direct and elegant. Let’s take a look at the definition of enumerate first:

def enumerate(collection):
      'Generates an indexed series:  (0,coll[0]), (1,coll[1]) ...'
           i = 0       
           it = iter(collection)       
       while 1:       
           yield (i, it.next())       
           i += 1

enumerate will form an array or list into an index sequence. It makes it more convenient for us to obtain the index and index content as follows:

for index，text in enumerate(list)):     
    print index ,text

Introduced in the cookbook, if you want to calculate the number of lines in the file, you can write like this:

count = len(open(thefilepath,‘rU’).readlines())

The previous method Simple, but may be slow, and may not even work when the file is large. The following loop reading method is more suitable.

Count = -1  For count,line in enumerate(open(thefilepath,‘rU’))：      
    Pass Count += 1

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