Not wishing to put words in the mouths of the creators, but there are a few reasons why one might target 2.7 rather than 3.x: 1. 2.7 is a stable target. There

Not wishing to put words in the mouths of the creators, but there are a few reasons why one might target 2.7 rather than 3.x: 1. 2.7 is a stable target. There will be no further features added to the 2.x series. 2. 2.7 is a known target. Other experiments like PyPy have already tried many paths to improve 2.7, so what doesn't work is reasonably well known. 3. 2.7 is a widely deployed target. This is less important from an "adoption" point of view, more so that there is a lot of software written that targets 2.x, meaning there's more software to test with. 4. Finally, I suspect much of Dropbox's codebase is 2.7[1], and since this is an effort to improve things for Dropbox, it makes sense to spend the initial efforts there :) [1] checking the version of Python bundled with the Dropbox client confirms that it, at least, is 2.7 /Applications/Dropbox.app/Contents/MacOS/python --version Python 2.7.3