1Mangesh1 Python Environment Management
Virtual environments, dependency management, and Python version control.
venv (Built-in)
# Create virtual environment
python -m venv .venv
python3 -m venv .venv
# Activate
source .venv/bin/activate # Linux/macOS
.venv\Scripts\activate # Windows
# Deactivate
deactivate
# Install packages
pip install requests flask
pip install -r requirements.txt
# Freeze dependencies
pip freeze > requirements.txt
# Upgrade pip
pip install --upgrade pip
requirements.txt
# Pinned versions (production)
flask==3.0.0
requests==2.31.0
sqlalchemy==2.0.23
# Ranges (library development)
flask>=3.0,<4.0
requests~=2.31 # Compatible release (>=2.31, <3.0)
# With extras
fastapi[all]==0.104.0
# From git
git+https://github.com/user/repo.git@main#egg=package
# Separate dev dependencies
pip install -r requirements.txt
pip install -r requirements-dev.txt
Poetry
# Install Poetry
curl -sSL https://install.python-poetry.org | python3 -
# Create new project
poetry new my-project
poetry init # In existing project
# Add dependencies
poetry add requests flask
poetry add pytest --group dev
poetry add "sqlalchemy>=2.0,<3.0"
# Remove dependency
poetry remove requests
# Install all dependencies
poetry install
poetry install --without dev
# Update dependencies
poetry update
poetry update requests # Single package
# Show dependencies
poetry show
poetry show --tree
# Run command in virtualenv
poetry run python main.py
poetry run pytest
# Activate shell
poetry shell
# Build & publish
poetry build
poetry publish
# Export to requirements.txt
poetry export -f requirements.txt --output requirements.txt
poetry export -f requirements.txt --without-hashes
pyproject.toml (Poetry)
[tool.poetry]
name = "my-project"
version = "1.0.0"
description = "My project"
authors = ["Name <email@example.com>"]
python = "^3.11"
[tool.poetry.dependencies]
python = "^3.11"
flask = "^3.0"
sqlalchemy = "^2.0"
[tool.poetry.group.dev.dependencies]
pytest = "^8.0"
ruff = "^0.1"
mypy = "^1.7"
[tool.poetry.scripts]
serve = "my_project.main:app"
uv (Fast Python Package Manager)
# Install uv
curl -LsSf https://astral.sh/uv/install.sh | sh
# Create virtual environment
uv venv
# Install packages (10-100x faster than pip)
uv pip install requests flask
uv pip install -r requirements.txt
# Sync from lock file
uv pip sync requirements.txt
# Compile requirements (resolve + lock)
uv pip compile requirements.in -o requirements.txt
# Create project
uv init my-project
# Add dependency
uv add requests
uv add pytest --dev
# Run
uv run python main.py
pyenv (Python Version Management)
# Install pyenv
curl https://pyenv.run | bash
# List available versions
pyenv install --list | grep "3\."
# Install Python version
pyenv install 3.12.1
pyenv install 3.11.7
# Set global default
pyenv global 3.12.1
# Set local version (per directory)
pyenv local 3.11.7 # Creates .python-version
# List installed
pyenv versions
# Uninstall
pyenv uninstall 3.10.0
Pipenv
# Install
pip install pipenv
# Create environment + install
pipenv install
pipenv install requests
pipenv install pytest --dev
# Run in environment
pipenv run python main.py
pipenv shell
# Lock dependencies
pipenv lock
# Install from lock file
pipenv install --deploy
# Show dependency graph
pipenv graph
conda
# Create environment
conda create -n myenv python=3.12
conda create -n myenv python=3.12 numpy pandas
# Activate/deactivate
conda activate myenv
conda deactivate
# Install packages
conda install numpy pandas
conda install -c conda-forge package-name
# List environments
conda env list
# Export environment
conda env export > environment.yml
# Create from file
conda env create -f environment.yml
# Remove environment
conda env remove -n myenv
Common Issues
# "pip not found" after creating venv
python -m pip install --upgrade pip
# Permission errors
pip install --user package-name
# Conflicting versions
pip install --force-reinstall package==1.0
# Clear pip cache
pip cache purge
# Check what's outdated
pip list --outdated
# Verify installation
python -c "import package; print(package.__version__)"
Reference
For comparison and migration guides: references/tools.md