Virtual Environment and pip in Python

In this lesson: Create and activate venv, install packages with pip and use requirements.txt — commands for Windows and Linux. In Hindi & English.

Why a virtual environment?

Imagine two projects on one laptop: a school report app that needs pandas 1.5 and a new dashboard that needs pandas 2.2. If both use the same global Python, installing one breaks the other. A virtual environment (venv) is a private folder of packages for each project.

Step 1: create the environment

Open a terminal inside your project folder (in VS Code: Terminal → New Terminal) and run:

# Windows
py -m venv .venv

# macOS / Linux
python3 -m venv .venv

This creates a hidden folder .venv with its own copy of the Python launcher and pip. The name .venv is a common convention – VS Code detects it automatically.

Step 2: activate it

After activation the prompt starts with (.venv). Check that Python now comes from the project folder:

(.venv) $ python -m pip --version
(.venv) $ pip list

A fresh environment contains only pip – none of your global packages. (Your version numbers will differ; this run used Python 3.13.)

Step 3: install packages with pip

pip install requests              # latest version
pip install requests==2.32.3      # exact version
pip install "pandas>=2,<3"        # any 2.x version
pip install --upgrade requests    # update
pip uninstall requests            # remove
pip show requests                 # details: version, location, dependencies

Installing requests also installs the packages it depends on. This is what pip freeze showed after pip install requests==2.32.3:

Step 4: share the project with requirements.txt

# save the exact versions you are using
pip freeze > requirements.txt

# on another computer (after creating and activating a new .venv)
pip install -r requirements.txt

Your Python code can also check which versions are installed – useful in bug reports:

import sys
from importlib import metadata

print("Python", sys.version.split()[0])
print("inside a venv:", sys.prefix != sys.base_prefix)
for pkg in ["pip", "not-a-real-package"]:
    try:
        print(pkg, metadata.version(pkg))
    except metadata.PackageNotFoundError:
        print(pkg, "is not installed")

Step 5: keep .venv out of Git

The .venv folder is large and specific to your computer. Never upload it or copy it to another PC. Commit requirements.txt instead and add this line to .gitignore:

.venv/
__pycache__/

A clean project layout

school-report/
├── .venv/              ← not committed
├── .gitignore
├── requirements.txt
├── README.md
├── report.py
└── data/
    └── marks.csv

Common errors and fixes

Practice tasks

1. Create a folder weather-app, make a venv, install requests and save requirements.txt.
2. Delete .venv and rebuild the environment only from requirements.txt.
3. Run check_env.py inside and outside the venv and compare the “inside a venv” line.
4. Select the .venv interpreter in VS Code and run a file with the Run button.

Summary

• One project = one .venv: python -m venv .venv.
• Activate before working; the prompt shows (.venv).
• Install with python -m pip install; record versions with pip freeze > requirements.txt.
• Commit requirements.txt, ignore .venv.