\n appending at the end of each line

Question

I am writing lines one by one to an external files. Each line has 9 columns separated by Tab delimiter. If i split each line in that file and output last column, i can see \\n being appended to the end of the 9 column. My code is:

#!/usr/bin/python

with open("temp", "r") as f:
    for lines in f:
        hashes = lines.split("\t")
        print hashes[8]  

The last column values are integers, either 1 or 2. When i run this program, the output i get is,

['1\n']
['2\n']  

I should only get 1 or 2. Why is '\\n' being appended here?

I tried the following check to remove the problem.

with open("temp", "r") as f:
    for lines in f:
            if lines != '\n':
                    hashes = lines.split("\t")
                    print hashes[8]  

This too is not working. I tried if lines != ' ' . How can i make this go away? Thanks in advance.

Answer 1

Try using strip on the lines to remove the \\n (the new line character). strip removes the leading and trailing whitespace characters.

with open("temp", "r") as f:
    for lines in f.readlines():
        if lines.strip():
            hashes = lines.split("\t")
            print hashes[8]  

Answer 2

\\n is the newline character, it is how the computer knows to display the data on the next line. If you modify the last item in the array hashes[-1] to remove the last character, then that should be fine.

Answer 3

Depending on the platform, your line ending may be more than just one character. Dos/Windows uses "\\r\\n" for example.

def clean(file_handle):
    for line in file_handle:
        yield line.rstrip()

with open('temp', 'r') as f:
    for line in clean(f):
        hashes = line.split('\t')
        print hashes[-1]

I prefer rstrip() for times when I want to preserve leading whitespace. That and using generator functions to clean up my input.

Answer 4

Because each line has 9 columns, the 8th index (which is the 9th object) has a line break, since the next line starts. Just take that away:

print hashes[8][:-1]