# Environment set up


Management of virtual environments in python is a detailed and complex topic which is well beyond the scope of these documents. However, we do give a simple example of setting up a virtual environment through the linux command window. There are many ways to do this, this is only one!

These instructions demonstrate how to set up a new environment on ubuntu from scratch.
These were tested on Ubunutu 18.04 but something very similar should work on most linux versions.

```bash
# optional: start a new screen session. This allows you to easily come back to this session later
# see here: https://linuxize.com/post/how-to-use-linux-screen/
screen -S TopasOpt

# check python version:
python3 -V
# should be >= 3.8 - update if you need to:
sudo apt install python3.8
# the above command will by default install python to the symbolic link python3.8
# you can google how to change this if you want to!

# make virtual environment:
python3.8 -m venv TopasOptVenv
# activate it:
source TopasOptVenv/bin/activate

# Make sure the version of your pip and setuptools is sufficient for manylinux2014 wheels.
# thank to this answer:
# https://stackoverflow.com/questions/64095094/command-python-setup-py-egg-info-failed-with-error-code-1-in-tmp
pip3 install -U pip
pip3 install -U setuptools

# install TopasOpt
pip install TopasOpt
# test installation:
python3  # enter a python session
import TopasOpt
TopasOpt.__version__  # just to check it's there - should print e.g. 0.0.2
exit()  # exit python session.
```

you should now be able to set up and run the examples.

a few tips:

```bash
# to deactivate the virtual environment
deactivate
# to leave the screen session
# hold ctrl, press a, release, then press d
# to reneter the screen session
screen -r TopasOpt  # or whatever name you gave this session
# to exit and terminate screen session
exit # if you are not inside the screen session when you type this you will kill your main sesson instead!
```