Python file.write creating extra carriage return

Question

I'm writing a series of SQL statements to a file using python. The template string looks like:

store_insert = '\tinsert stores (storenum, ...) values (\'%s\', ...)' 

I'm writing to the file like so:

for line in source:     line = line.rstrip()     fields = line.split('\t')     script.write(store_insert % tuple(fields))     script.write(os.linesep) 

However, in the resulting output, I see \r\r\n at the end of each line, rather than \r\n as I would expect. Why?

Answer 1

\n is converted to os.linesep for files opened in text-mode. So when you write os.linesep to a text-mode file on Windows, you write \r\n, and the \n gets converted resulting in \r\r\n.

See also the docs:

Do not use os.linesep as a line terminator when writing files opened in text mode (the default); use a single '\n' instead, on all platforms.

Answer 2

With Python 3

open() introduces the new parameter newline that allows to specify a string which any occurrence of \n will be translated to.

Passing an empty string argument newline='' disables the translation, leaving the new line char as it is. Valid for text mode only.

From the documentation

On output, if newline is None, any '\n' characters written are translated to the system default line separator, os.linesep. If newline is '', no translation takes place. If newline is any of the other legal values, any '\n' characters written are translated to the given string.