Python VirtualEnv
A virtual environment gives one project its own installed packages. It helps avoid changing unrelated projects when a dependency needs another version.
Understand the idea
On Windows, create .venv with py -m venv .venv. You can run its interpreter directly without activation. Activation only adjusts the current shell's PATH and prompt; it is not required for the environment to work. Keep .venv out of source control and record dependencies instead of copying the environment folder between computers.
Where to try it
Run these commands in a local Windows terminal, not inside a Python source file. They require a local Python installation. The online text runner does not provide an operating-system shell.
A worked example
py -m venv .venv
.venv\Scripts\python.exe -m pip --version
Read the result
Run these in the project terminal. The second command should report pip from the newly created environment.
Try one change
Run .venv\Scripts\python.exe -c "import sys; print(sys.executable)" and verify the interpreter location.