CodeBlanks Logo Icon CodeBlanks
Login Register

Virtual environment

Learn to create virtual environments with venv.

Virtual environment

A virtual environment creates a separate Python directory for a project. Packages installed there do not pollute the global Python; each project gets its own dependency tree.

python -m venv .venv

The command creates a fresh Python copy in the .venv/ directory. When activated, pip install writes only into this directory and leaves global packages untouched.

venv.EnvBuilder

venv.EnvBuilder is the class that creates a virtual environment from Python code. The with_pip=True parameter also installs pip; clear=True wipes an existing directory.

import venv

builder = venv.EnvBuilder(with_pip=True)
builder.create(".venv")

EnvBuilder does the same job as the python -m venv command line, but it can be called from scripts. This is handy for writing automated setup commands.

Practice Print the type of the EnvBuilder object

Start with import venv. Create a builder object with builder = venv.EnvBuilder(with_pip=False). Print the class name of the object with print(type(builder).__name__).

Starter code

main.py
# bring in the venv module
# create an EnvBuilder with with_pip=False
# print the class name of the builder object

Sample solution

main.py
import venv

builder = venv.EnvBuilder(with_pip=False)
print(type(builder).__name__)

Expected output

EnvBuilder

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What does python -m venv .venv do?

  • Creates a virtual environment Correct answer
  • Builds a wheel
  • Uploads the package to PyPI
  • Freezes dependencies

Explanation: The venv command creates a virtual environment in .venv.

2 Complete the EnvBuilder call

Question 
import venv

builder = venv.____(with_pip=True)
Answer 
import venv

builder = venv.EnvBuilder(with_pip=True)

Explanation: EnvBuilder is the class that creates virtual environments.

3 Match the venv concepts

Term Meaning
venv Virtual env module
EnvBuilder Class that builds envs
with_pip Also installs pip
.venv Env directory

All lessons in Advanced

1 Advanced decorators

  1. Parameterized decorator
  2. Class decorator
  3. functools
  4. functools.partial
  5. functools.reduce
  6. Summary - Advanced decorators

2 Type hints

  1. Basic hints
  2. Optional and Union
  3. typing.List and Dict
  4. Callable
  5. TypeVar
  6. Summary - Type hints

3 Pytest

  1. pytest basics
  2. assert
  3. fixture
  4. parametrize
  5. monkeypatch
  6. Summary - Pytest

4 Mocking

  1. unittest.mock
  2. patch
  3. MagicMock
  4. side_effect
  5. assert_called
  6. Summary - Mocking

5 Async basics

  1. async/await
  2. asyncio.run
  3. async def
  4. await asyncio.sleep
  5. create_task
  6. Summary - Async basics

6 Asyncio

  1. gather
  2. wait
  3. Queue
  4. Lock
  5. Semaphore
  6. Summary - Asyncio

7 HTTP and aiohttp

  1. urllib
  2. aiohttp.ClientSession
  3. async get
  4. async post
  5. JSON response
  6. Summary - HTTP and aiohttp

8 SQLAlchemy

  1. Engine
  2. Session
  3. Defining models
  4. Column and type
  5. Query
  6. Summary - SQLAlchemy

9 FastAPI

  1. FastAPI app
  2. @app.get
  3. Pydantic model
  4. Path parameter
  5. Query parameter
  6. Summary - FastAPI

10 Pydantic

  1. BaseModel
  2. Field
  3. validator
  4. Config
  5. parse_obj
  6. Summary - Pydantic

11 Design patterns

  1. Singleton
  2. Factory
  3. Strategy
  4. Observer
  5. Decorator
  6. Summary - Design patterns

12 Logging

  1. logging.getLogger
  2. Log levels
  3. basicConfig
  4. FileHandler
  5. dictConfig
  6. Summary - Logging

13 Packaging

  1. pyproject.toml
  2. setuptools
  3. Virtual environment
  4. pip install
  5. requirements.txt
  6. Summary - Packaging

14 Advanced final

  1. Project design
  2. Async layer
  3. SQLAlchemy layer
  4. FastAPI layer
  5. Putting it together