This Python VirtualEnv lesson is for a beginner. Read the short notes, run each example, then change one name or number and run it again.
A virtual environment is a private folder of Python and packages for one project. python -m venv .venv creates it.
Activate it before pip install. Each project then keeps its own versions, and an upgrade in one folder does not break another.
Example 1: Start here
Commit requirements.txt, not the .venv folder.
print("python -m venv .venv") # print writes this; the quotes are not shown
print("Then activate the environment and run pip.")
Example 2: Read a fake environment name
A virtual environment is a folder that holds one project’s packages.
import sys # load a tool that comes with Python
print(sys.prefix.endswith("venv") or True) # and needs both tests; or needs one
print("Create one with: python -m venv .venv")
Example 3: Pick an interpreter
After you activate the environment, python means the interpreter inside that folder.
folder = ".venv" # text
print(folder + "/bin/python")
Example 4: Keep the project list
Install project packages only after the environment is active, so they do not mix with other projects.
packages = ["requests"] # a list; the values stay in this order
print("Install inside the environment:", ", ".join(packages)) # join the pieces into one text
Commit requirements.txt, not the .venv folder.
