Vfrdtyky

I am reading a file in Python line by line and I need to know which line is the last one while reading,something like this:

 f = open("myfile.txt")

 for line in f:

    if line is lastline:

       #do smth

From the examples I found it involves seeks and complete file readouts to count lines,etc.Can I just detect that the current line is the last one? I tried to go and check for "n" existence ,but in many cases the last lines is not followed by backslash N.

Sorry if my question is redundant as I didn't find the answer on SO

secondLastLine = None

lastLine = None

with open("myfile.txt") as infile:

    secondLastLine, lastLine = infile.readline(), infile.readline()

    for line in infile:

        # do stuff

        secondLastLine = lastLine

        lastLine = line



# do stuff with secondLastLine

import os

path = 'myfile.txt'

size = os.path.getsize(path)

with open(path) as f:

    for line in f:

        size -= len(line)

        if not size:

            print('this is the last line')

            print(line)

Check if line is the last line:

with open("in.txt") as f:

    lines = f.readlines()

    last = lines[-1]

    for line in lines:

        if line is last:

            print id(line),id(last)

            # do work on lst line

        else:

            # work on other lines

If you want the second last line use last = lines[-2]

Or simply:

with open("in.txt") as f:

    lines = f.readlines()

    last = lines[-1]

    for line in lines[:-1]:

        # work on all but last line

    # work on last

One thing you could try is to try to get the next line, and catch the exception if it arises, because AFAIK python iterators don't have inbuilt hasNext method.

You could use the itertools pairwise recipe;

with open('myfile.txt') as infile:

    a,b = itertools.tee(infile)

    next(b, None)

    pairs = zip(a,b)

    lastPair = None

    for lastPair in pairs:

        pass

secondLastLine = lastPair[0]

# do stuff with secondLastLine

It's an old question, but if you want to allow empty last lines, this is better:

with open("myfile.txt") as f:

    while True:

        line = f.readline()

        # do smth

        if line[-1:] != 'n':

            # do smth with the last line

            break

or more readable (but a little bit slower):

with open("myfile.txt") as f:

    while True:

        line = f.readline()

        # do smth

        if not line.endswith('n'):

            # do smth with the last line

            break