How do I stop having carriage returns added to my file output in Python?

Question

I'm trying to parse a BMP file, do some changes and then reassemble a new BMP using Python.

The carriage return seems to be a huge problem. When I open the bitmap file using Notepad++ and search for "\r', the character does not exist. I read the file in Python (readData = fileIn.read()) and try searching using readData.find('\r') it returns -1. Searching for "\n" works fine. All is good for now.

When I try to write this exact same block of text into a new BMP using fileOut.write(readData) and I use Notepad++ to search for "\r", I am able to find it (twice, each corresponding to the preexisting "\n" characters).

Is there a way to write this block of data to a new BMP without "\r" being added automatically? I've tried applying .strip() and .replace('\r','') to the string before writing it to the new file.

Answer 1

You're probably opening the file as text (the default) when you want to open it as binary.

open("example.bmp", "rb") # to [r]ead as [b]inary
open("example.bmp", "wb") # to [w]rite as [b]inary

From the documentation:

The default is to use text mode, which may convert '\n' characters to a platform-specific representation on writing and back on reading. Thus, when opening a binary file, you should append 'b' to the mode value to open the file in binary mode, which will improve portability.

Answer 2

You are opening the file in text mode, while you need binary mode. Find more about open() here: http://docs.python.org/library/functions.html