How can I force Python's file.write() to use the same newline format in Windows as in Linux ("rn" vs. "n")?

Question

I have the simple code:

f = open('out.txt','w')
f.write('line1n')
f.write('line2')
f.close()

Code runs on windows and gives file size 12 bytes, and linux gives 11 bytes
The reason is new line

In linux it’s n and for win it is rn

But in my code I specify new line as n. The question is how can I make python keep new line as n always, and not check the operating system.

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Answer 1

You need to open the file in binary mode i.e. wb instead of w. If you don’t, the end of line characters are auto-converted to OS specific ones.

Here is an excerpt from Python reference about open().

The default is to use text mode, which may convert ‘n’ characters to a platform-specific representation on writing and back on reading.

Answer 2

You can still use the textmode and when you print a string, you remove the last character before printing, like this:

f.write("FooBar"[:-1])

Tested with Python 3.4.2.

Edit: This does not work in Python 2.7.

Answer 3

This is an old answer, but the io.open function lets you to specify the line endings:

import io
with io.open('tmpfile', 'w', newline='rn') as f:
    f.write(u'foonbarnbazn')

Answered By: Leonardo

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