Reading specific lines only

Question

I\'m using a for loop to read a file, but I only want to read specific lines, say line #26 and #30. Is there any built-in feature to achieve this?

Thanks

Answer 1

For the sake of offering another solution:

import linecache
linecache.getline('Sample.txt', Number_of_Line)

I hope this is quick and easy :)

Answer 2

For the sake of completeness, here is one more option.

Let's start with a definition from python docs:

slice An object usually containing a portion of a sequence. A slice is created using the subscript notation, [] with colons between numbers when several are given, such as in variable_name[1:3:5]. The bracket (subscript) notation uses slice objects internally (or in older versions, __getslice__() and __setslice__()).

Though the slice notation is not directly applicable to iterators in general, the itertools package contains a replacement function:

from itertools import islice

# print the 100th line
with open('the_file') as lines:
    for line in islice(lines, 99, 100):
        print line

# print each third line until 100
with open('the_file') as lines:
    for line in islice(lines, 0, 100, 3):
        print line

The additional advantage of the function is that it does not read the iterator until the end. So you can do more complex things:

with open('the_file') as lines:
    # print the first 100 lines
    for line in islice(lines, 100):
        print line

    # then skip the next 5
    for line in islice(lines, 5):
        pass

    # print the rest
    for line in lines:
        print line

And to answer the original question:

# how to read lines #26 and #30
In [365]: list(islice(xrange(1,100), 25, 30, 4))
Out[365]: [26, 30]

Answer 3

@OP, you can use enumerate

for n,line in enumerate(open("file")):
    if n+1 in [26,30]: # or n in [25,29] 
       print line.rstrip()

Answer 4

I think this would work

 open_file1 = open("E:\\test.txt",'r')
 read_it1 = open_file1.read()
 myline1 = []
 for line1 in read_it1.splitlines():
 myline1.append(line1)
 print myline1[0]