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--- deptlab:python_virtual_env [2021/10/21 21:14] – localadmin
+++ deptlab:python_virtual_env [2024/09/17 17:18] (current) – [Using Virtual Environments] localadmin
@@ Line 24: / Line 24: @@
 There are no limits to the number of environments you can have since they’re just directories containing a few scripts. Plus, they’re easily created using the virtualenv or pyenv command line tools.
+===== Using Virtual Environments =====
+CS Lab and shared research computers should already have the ''venv'' module from the standard library installed.
+Start by making a new directory to work with:
+$ mkdir python-virtual-environments && cd python-virtual-environments
+Create a new virtual environment inside the directory:
+''python3 -m venv project_1_env''
+**Note:** By default, this will not include any of your existing site packages.
+In the above example, this command creates a directory called project_1_env, which contains a directory structure similar to this:
+<code>
+├── bin
+│   ├── activate
+│   ├── activate.csh
+│   ├── activate.fish
+│   ├── easy_install
+│   ├── easy_install-3.8
+│   ├── pip
+│   ├── pip3
+│   ├── pip3.8
+│   ├── python -> python3.
+│   ├── python3 -> /usr/bin/python3
+├── include
+├── lib
+│   └── python3.8
+│       └── site-packages
+├── pyvenv.cfg
+└── share
+</code>
+Here’s what each folder contains:
+  * bin: files that interact with the virtual environment
+  * include: C headers that compile the Python packages
+  * lib: a copy of the Python version along with a site-packages folder where each dependency is installed
+In order to use this environment’s packages/resources in isolation, you need to “activate” it. To do this, just run the following:
+  $ source project_1_env/bin/activate
+  (project_1_env) $
+Notice how your prompt is now prefixed with the name of your environment (''project_1_env'', in this case). This is the indicator that ''project_1_env'' is currently active, which means <color #ed1c24>the python executable will only use this environment’s packages and settings.</color>
+Now you can use pip to install packages (large packages may take a while to install).
+To go back to the “system” context, execute a deactivate:
+  (env) $ deactivate
+  $
+Now your shell session is back to normal, and the python command refers to the global Python install. Remember to do this whenever you’re done using a specific virtual environment.
+Using Virtual Environment makes it east to reset your Python environment if you need to use a different set of packages.  Just delete the old environment and create a new one.
+**Be sure to cleanup/delete unused temp files and environments when done using them.**
+===== Tips for Using a Python3 IDE with Virtual Environments =====
+==== Using Spyder in the 244 Lab ====
+  - Activate (start) your virtual environment.
+  - Run spyder
+  - Go to Tools --> preferences --> python Interpreter and select the python file from the virtual env you want to link to Spyder ex : /home/you/envs/your_env/bin/python
+==== Preferred Method on Research Computers: Spyder Method 1 (Use with tensorflow) ====
+To use Spyder.
+  - Activate (start) your virtual environment.
+  - Install the needed packages with pip
+  - Install Spyder into your environment using pip install spyder.
+  - Then start spyder from the environment command line with the command spyder.
+==== Spyder Method 2 (Doesn't work well with tensorflow) ====
+  - Activate (start) your virtual environment.
+  - Run spyder from the environment (after source activate)
+  - Go to Tools --> preferences --> python Interpreter and select the python file from the env you want to link to spyder ex : /home/you/envs/your_env/bin/python
+ [[https://realpython.com/python-virtual-environments-a-primer/|See... Using Python Virtual Environments]] for more detail