How to setup a virtual environnement in Scala?

Author: mariogalic

_overviews/scala3-book/scala-for-python-devs.md

@@ -1291,6 +1291,36 @@ Follow the links below for more details:
 - Infix methods
 - Macros and metaprogramming
 
+## How to setup a virtual environnement in Scala?
+
+In Python there is a common practice of creating an isolated environnement for a particular project. For example, say we are working on application `myapp`, then using `venv` Python module we might do
+
+```
+cd myapp
+python3 -m venv myapp-env
+source myapp-env/bin/activate
+pip install -r requirements.txt
+```
+
+This installs all the dependencies under project's directory `myapp/myapp-env` and alters the shell environmental variable `PATH` to look up dependencies from `myapp-env`. Another popular approach is to use Pipenv
+
+```
+cd myapp
+pipenv shell
+pipenv install
+```
+
+which makes use of `Pipfile` and corresponding lock file to manage dependencies.
+
+Key difference in Scala is that project's dependencies are not installed per project, and hence potentially same dependency of the same version is duplicated across multiple projects, but instead dependencies are installed inside a central local repository which is reused across projects. Dependency of particular version is installed only once and then reused across different projects that require it. For example using `sbt` build tool we specify dependencies inside `build.sbt` file (which is conceptually similar to `Pipfile`) under `libraryDependencies`, then executing
+
+```
+cd myapp
+sbt compile
+```
+
+downloads all the dependencies under the local repository. The location of the local repository can be queried with `show csrCacheDirectory` inside `sbt` shell. Note by using `sbt` each project gets its own isolated environment without the need for lock files or modification of the shell environnement. All the necessary paths are managed by the build tool itself. 
+
 [collections-classes]: {% link _overviews/scala3-book/collections-classes.md %}
 [concurrency]: {% link _overviews/scala3-book/concurrency.md %}
 [contextual]: {% link _overviews/scala3-book/ca-contextual-abstractions-intro.md %}