在python上尾巴 最佳性能实施

Question

I'm newbie to programming and in Python as well.
I wrote a function that implements the unix's tail:

def tail(file):
    strin = open(file, 'r')
    lis = strin.readlines()
    lastline = lis[-1]
    return lastline
    strin.close()

But I think that it is not optimal in performance.
How can I improve?

Answer 1

You can use this Recipe from Collections.deque

def tail(filename, n=10):
    'Return the last n lines of a file'
    return deque(open(filename), n)

Refer this :- https://docs.python.org/2/library/collections.html#deque-recipes

Answer 2

There's no need to store all the lines since you only want the last one:

lis = strin.readlines()
lastline = lis[-1]

More efficient is as per the answers to Iterate through Python list and do something on last element :

for line in open(file, 'r'):
    pass
else:
    return line

(I was not aware of the Collections.deque solution and I agree it's better, also parameterizable for n lines)

Answer 3

There are a couple of problems with your code. First you are closing the file after the return. Everything after the return statement will not be reached. Second, when you're working with files, you should use with . It opens your file, and when it leaves the block it will close it for you. And at last, you can merge three lines to an oneliner.

I would wrote it like this:

def tail(file):
    with open(file, 'r') as o:
        return o.readlines()[-1]