file.readlines leaving blank lines

Question

I have read that file.readlines reads the whole file line by line and stores it in a list. If I have a file like so -

Sentence 1
Sentence 2
Sentence 3

and I use readlines to print each sentence like so -

file = open("test.txt") 
for i in file.readlines():
    print i

The output is

Sentence 1

Sentence 2

Sentence 3

My question is why do I get the extra line between each sentence and how can I get rid of it?

UPDATE

I found that using i.strip also removes the extra lines. Why does this happen? As far as I know, split removes the white spaces at the end and beginning of a string.

falsetru · Accepted Answer · 2013-11-04T06:26:59.533

11

file.readlines() return list of strings. Each string contain trailing newlines. print statement prints the passed parameter with newlnie.; That's why you got extra lines.

To remove extra newline, use str.rstrip:

print i.rstrip('\n')

or use sys.stdout.write

sys.stdout.write(i)

BTW, don't use file.readlines unless you need all lines at once. Just iterate the file.

with open("test.txt") as f:
    for i in f:
        print i.rstrip('\n')
        ...

UPDATE

In Python 3, to prevent print prints trailing newline, you can use print(i, end='').

In Python 2, you can use same feature if you do : from __future__ import print_function

Answer to UPDATE

Tabs, Newlines are also considers as whitespaces.

>> ' \r\n\t\v'.isspace()
True

edited Nov 04 '13 at 06:26

answered Nov 04 '13 at 06:05

falsetru

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...and then your print command is adding the second newline I guess – James Sefton Nov 04 '13 at 06:06
`rstrip("\n")` would be enough since the file was opened in text mode. – Tim Pietzcker Nov 04 '13 at 06:08
@TimPietzcker, You're right. I edited the answer according to your comment. Thank you. – falsetru Nov 04 '13 at 06:09
Or, `print(i, end='')` if the OP is on Python 3; or `from __future__ import print_function` if on Python 2.x – Burhan Khalid Nov 04 '13 at 06:17
Why were you doing `rstrip("\r\n")` ? There is no `\r` at the end of the sentence right ? – MayankJain Nov 04 '13 at 06:18
@Mayank, I updated answer. Maybe you are seeing old revision of the answer. `\r` will not appear unless you open the file with binary mode (`b`). – falsetru Nov 04 '13 at 06:22

score 1 · Answer 2 · answered Nov 04 '13 at 06:06

file.readlines()

(and also file.readline()) includes the newlines.

Do

print i.replace('\n', '')

if you don't want them.

It may seem weird to include the newline at the end of the line, but this allows, for example, you to tell whether the last line has a newline character or not. That case in tricky in many languages' I/O.

score 1 · Answer 3 · answered Nov 04 '13 at 06:34

1

The below will strip the newline for you.

i = i.rstrip("\n") #strips newline

Hope this helps.

answered Nov 04 '13 at 06:34

fscore

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Thinh Le · Answer 4 · 2019-06-14T09:27:12.283

0

This worked out for me with Python 3. I found rstrip() function really useful in these situations

for i in readtext:
    print(i.rstrip())

edited Jun 14 '19 at 09:27

answered Jun 14 '19 at 09:05

Thinh Le

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Please add description – Wang Liang Jun 14 '19 at 09:22
Hi, I am new to this. May I ask how I can add description? – Thinh Le Jun 14 '19 at 09:28

score 0 · Answer 5 · answered Nov 07 '20 at 18:38

0

with open(txtname, 'r') as txtfile:
    lines = txtfile.readlines()
    lines = [j for j in lines if j != '\n']
with open(outname, 'w') as outfile:
    outfile.writelines(lines)

answered Nov 07 '20 at 18:38

Burak

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file.readlines leaving blank lines

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