Adding python version and pyenv virtualenv name to bash prompt? - bash

Question

I'm trying to achieve a PS1 that will output [3.6.5#BooksHerokuDjango ~]$
My .bashrc has this:
export PYENV_ROOT="$HOME/.pyenv"
export PATH="$PYENV_ROOT/bin:$PATH"
if command -v pyenv 1>/dev/null 2>&1; then
eval "$(pyenv init -)"
fi
eval "$(pyenv virtualenv-init -)"
export PYENV_VIRTUALENV_DISABLE_PROMPT='1'
function __python_prompt {
version_number=`python -V | cut -d " " -f2-`
version_name=`pyenv version-name`
at='#'
python_prompt=$version_number$at$version_name
echo $python_prompt
}
PS1="[\$(__python_prompt) \W]\$ "
export PS1
I have the following pyenv versions:
[3.6.5#BooksHerokuDjango ~]$ pyenv versions
system
2.7.14
2.7.14/envs/HackerNewsHerokuDjango
3.2
3.2/envs/BlogHerokuDjango
3.6.5
3.6.5/envs/BooksHerokuDjango
3.6.5/envs/PortfolioDjango
BlogHerokuDjango
* BooksHerokuDjango (set by PYENV_VERSION environment variable)
HackerNewsHerokuDjango
PortfolioDjango
When I change the virtualenv like so:
[3.6.5#BooksHerokuDjango ~]$ pyenv activate HackerNewsHerokuDjango
Python 2.7.14
[#HackerNewsHerokuDjango ~]$
The PS1 doesn't output like this [2.7.14#HackerNewsHerokuDjango ~]$
But then I change the virtualenv again:
Python 2.7.14
[#HackerNewsHerokuDjango ~]$ pyenv activate PortfolioDjango
[3.6.5#PortfolioDjango ~]$
I get the PS1 output that I wanted. What am I doing wrong for it to be inconsistent?