Why does python still work after being removed?

It turned out that the additional package python-minimal had python installed. One does then not only have to do:

sudo apt-get remove python

but also:

sudo apt-get remove python-minimal

Unfortunately, I have no Debian at hand to test, but anyway:

I think you did not really uninstall python. Package 'python2.7' is not installed, so not removed only means that a package python2.7 is not installed. But perhaps the name is different.

which python says /usr/bin/python. That is a clear sign that you have python installed. Here is the official package.

dpkg-query -l 'python*' should help in getting the name/version of the installed package.

apt-rdepends should tell you which packages rely on python.

You should probably look at the output of dpkg --get-selections | grep python to see all the installed python packages. There are a few packages for various different releases that may be installed on a system. Keep in mind that python is in the standard selections, so fully removing it will also remove other 'standard' packages like reportbug.