Handling \r\n vs \n newlines in python on Mac vs Windows
I have a python script that gave different output when run on a Windows machine and when run on a Mac. On digging deeper, I discovered that it was because when Python read in line breaks on the Mac (from a file), it read in \r\n, while somehow in Windows the \r disappears.
Thus, if I change every \n in the script to \r\n, it works fine on the Mac. But if I do that, it stops working on the Windows PC.
Is there an easy way to fix this problem?
Solution 1:
Different platforms have different codes for "new line". Windows have \r\n, Unix has \n, Old macs have \r and yes there are some systems that have \n\r too.
When you open a file in text mode in Python 3, it will convert all newlines to '\n' and be done with it.
infile = open("filename", 'r')
Text mode is default, so if you say nothing, it's text mode. But it's always better to be explicit:
infile = open("filename", 'rt')
If you don't want the translation of line endings to happen, open the file in binary mode:
infile = open("filename", 'rb')
In Python 2 it's different. There this conversion would only happen by default on Windows. If you wanted it to happen on other platforms, you could add the universal newline flag:
infile = open("filename", 'rU')
However, you say that you are on Python 3, and there it happens in text mode on all platforms, so adding the U flag should make no difference.
Solution 2:
'U' mode:
Python 2:
I guess it may depend on what you're reading from, but the built-in open() function takes a 'mode' parameter, and if you pass 'U' for the mode, Python 2 will take care of the newlines in a cross-platform way transparently. It requires that Python be built with universal newline support, but test it out!
https://docs.python.org/2/library/functions.html#open
Python 3:
In Python 3, the 'U' mode is the default behaviour, as the docs explain:
There is an additional mode character permitted,
'U', which no longer has any effect, and is considered deprecated. It previously enabled universal newlines in text mode, which became the default behaviour in Python 3.0. Refer to the documentation of the newline parameter for further details.
https://docs.python.org/3/library/functions.html#open