How to use 2to3 properly for python?

I have some code in python 2.7 and I want to convert it all into python 3.3 code. I know 2to3 can be used but I am not sure exactly how to use it.

Install the following module which adds the 2to3 command directly to entry_points.

pip install 2to3

As it is written on 2to3 docs, to translate an entire project from one directory tree to another, use:

2to3 --output-dir=python3-version/mycode -W -n python2-version/mycode

If you don't have 2to3 on your path, you can directly invoke lib2to3:

python -m lib2to3 directory\file.py

And as the docs (and other answers) mention, you can use some flags for more customization:

• the -w flag to enable writeback, which applies the changes to the file
• the -n to disable backups

(there are a few more flags; see the docs for more information.)

It's important to have a backup before running 2to3.

1. If you're using git, make a commit.
2. Otherwise, make a backup copy of your files.

First, run 2to3 in "soft mode" to see what it would actually do:

$ 2to3 /path/to/your/project

If you're happy with what it would do, you can then run 2to3 "for real":

$ 2to3 --write --nobackups /path/to/your/project

And now you have properly run 2to3 :)