pull out environment directions from contributor install guide

Author: munkm

content/how-tos/envs.md

@@ -0,0 +1,123 @@
+---
+title: How to set up a virtual environment
+---
+
+In this guide we summarize some key commands to set up a virtual environment
+with different tools in the scientific python ecosystem. 
+A virtual environment is a workspace into which you can install Python
+libraries, separate from what is being used by your operating system.
+
+The environment managers that are covered in this how-to guide include:
+- venv
+- conda
+- mamba
+- uv
+- pixi
+
+In each of these examples we'll create a new virtual environment related to our project called `science` 
+(you can use whichever name you prefer!). We'll activate the environment, install some dependencies, and see 
+an example of installing dependencies from a file. 
+
+### Set up a virtual environment with venv
+
+With venv we'll have our virtual environment associated with our project folder called `science`. 
+
+```
+python -m venv science
+```
+
+Start using it by activating it as follows:
+
+```
+source science/bin/activate
+```
+
+You are now ready to install Scientific Python packages using `pip`! For example:
+
+```
+pip install ipython numpy scipy
+```
+
+Often you'll interact with projects that have a specific list of dependencies (for development 
+environments, testing environments, or the project itself). You can install the list of dependencies
+with pip in your venv using: 
+
+```
+pip install -r requirements.txt
+```
+
+Remember to re-activate your environment every time you open a new terminal, using:
+
+```
+source science/bin/activate
+```
+
+### Set up a virtual environment using conda 
+
+With conda, we can create a new environment named science (-n is the same as passing --name):
+
+```
+conda create -n science
+```
+
+Start using your environment by activating it: 
+
+```
+conda activate science
+```
+
+You are now ready to install Scientific Python packages using `conda`!
+For example:
+
+```
+conda install ipython numpy scipy
+```
+
+Often you'll interact with projects that have a specific list of dependencies (for development 
+environments, testing environments, or the project itself). You can install the list of dependencies
+with conda in your environment using: 
+
+```
+conda install --file requirements.txt
+```
+
+Remember to re-activate your environment every time you open a new terminal:
+
+```
+conda activate science
+```
+
+### Set up a virtual environment using mamba 
+
+With mamba, like conda, we can create a new environment named science (-n is the same as passing --name):
+
+```
+mamba create -n science
+```
+
+Start using your environment by activating it: 
+
+```
+mamba activate science
+```
+
+You are now ready to install Scientific Python packages using `mamba`!
+For example:
+
+```
+mamba install ipython numpy scipy
+```
+
+Often you'll interact with projects that have a specific list of dependencies (for development 
+environments, testing environments, or the project itself). You can install the list of dependencies
+with mamba in your environment using: 
+
+```
+mamba install --file requirements.txt
+```
+
+Remember to re-activate your environment every time you open a new terminal:
+
+```
+mamba activate science
+```