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

enumeratewill 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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