Python daily improvement (7)-enumerate usage

Python cookbook Recipe 2.5. Counting Lines in a File,

A new function enumerate was found today. In general, if you want to traverse both the index and element of a list or array, write as follows:

For I in range (0, len (list )):
Print I, list [I], but this method is somewhat cumbersome. Using the built-in enumerrate function is more straightforward and elegant. Let's first look at the definition of enumerate:

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 combines an array or list into an index sequence. This makes it easier to obtain the index and index content as follows:

For index, text in enumerate (list )):
Print index, text

In cookbook, if you want to calculate the number of lines in the file, you can write it as follows:

Count = len (open (thefilepath, 'ru '). readlines ())

The preceding method is simple, but may be slow. When the file is large or cannot work, the following method is more suitable for reading cyclically.

Count =-1
For count, line in enumerate (open (thefilepath, 'ru ')):
Pass
Count + = 1

Vivilisa write in 03.19.2009