Install packages in a virtual environment using pip and venv#

This guide discusses how to create and activate a virtual environment using the standard library’s virtual environment tool venv and install packages. The guide covers how to:

  • Create and activate a virtual environment

  • Prepare pip

  • Install packages into a virtual environment using the pip command

  • Use and create a requirements file

Note

This guide applies to supported versions of Python, currently 3.8 and higher.

Note

This guide uses the term package to refer to a Distribution Package, which commonly is installed from an external host. This differs from the term Import Package which refers to import modules in your Python source code.

Important

This guide has the prerequisite that you are using an official Python version obtained from <https://www.python.org/downloads/>. If you are using your operating system’s package manager to install Python, please ensure that Python is installed before proceeding with these steps.

Create and Use Virtual Environments#

Create a new virtual environment#

venv (for Python 3) allows you to manage separate package installations for different projects. It creates a “virtual” isolated Python installation. When you switch projects, you can create a new virtual environment which is isolated from other virtual environments. You benefit from the virtual environment since packages can be installed confidently and will not interfere with another project’s environment.

Tip

It is recommended to use a virtual environment when working with third party packages.

To create a virtual environment, go to your project’s directory and run the following command. This will create a new virtual environment in a local folder named .venv:

python3 -m venv .venv

py -m venv .venv

The second argument is the location to create the virtual environment. Generally, you can just create this in your project and call it .venv.

venv will create a virtual Python installation in the .venv folder.

Note

You should exclude your virtual environment directory from your version control system using .gitignore or similar.

Activate a virtual environment#

Before you can start installing or using packages in your virtual environment you’ll need to activate it. Activating a virtual environment will put the virtual environment-specific python and pip executables into your shell’s PATH.

source .venv/bin/activate

.venv\Scripts\activate

To confirm the virtual environment is activated, check the location of your Python interpreter:

which python

where python

While the virtual environment is active, the above command will output a filepath that includes the .venv directory, by ending with the following:

.venv/bin/python

.venv\Scripts\python

While a virtual environment is activated, pip will install packages into that specific environment. This enables you to import and use packages in your Python application.

Deactivate a virtual environment#

If you want to switch projects or leave your virtual environment, deactivate the environment:

deactivate

Note

Closing your shell will deactivate the virtual environment. If you open a new shell window and want to use the virtual environment, reactivate it.

Reactivate a virtual environment#

If you want to reactivate an existing virtual environment, follow the same instructions about activating a virtual environment. There’s no need to create a new virtual environment.

Prepare pip#

pip is the reference Python package manager. It’s used to install and update packages into a virtual environment.

The Python installers for macOS include pip. On Linux, you may have to install an additional package such as python3-pip. You can make sure that pip is up-to-date by running:

python3 -m pip install --upgrade pip
python3 -m pip --version

Afterwards, you should have the latest version of pip installed in your user site:

pip 23.3.1 from .../.venv/lib/python3.9/site-packages (python 3.9)

The Python installers for Windows include pip. You can make sure that pip is up-to-date by running:

py -m pip install --upgrade pip
py -m pip --version

Afterwards, you should have the latest version of pip:

pip 23.3.1 from .venv\lib\site-packages (Python 3.9.4)

Install packages using pip#

When your virtual environment is activated, you can install packages. Use the pip install command to install packages.

Install a package#

For example,let’s install the Requests library from the Python Package Index (PyPI):

python3 -m pip install requests

py -m pip install requests

pip should download requests and all of its dependencies and install them:

Collecting requests
  Using cached requests-2.18.4-py2.py3-none-any.whl
Collecting chardet<3.1.0,>=3.0.2 (from requests)
  Using cached chardet-3.0.4-py2.py3-none-any.whl
Collecting urllib3<1.23,>=1.21.1 (from requests)
  Using cached urllib3-1.22-py2.py3-none-any.whl
Collecting certifi>=2017.4.17 (from requests)
  Using cached certifi-2017.7.27.1-py2.py3-none-any.whl
Collecting idna<2.7,>=2.5 (from requests)
  Using cached idna-2.6-py2.py3-none-any.whl
Installing collected packages: chardet, urllib3, certifi, idna, requests
Successfully installed certifi-2017.7.27.1 chardet-3.0.4 idna-2.6 requests-2.18.4 urllib3-1.22

Install a specific package version#

pip allows you to specify which version of a package to install using version specifiers. For example, to install a specific version of requests:

python3 -m pip install 'requests==2.18.4'

py -m pip install "requests==2.18.4"

To install the latest 2.x release of requests:

python3 -m pip install 'requests>=2.0.0,<3.0.0'

py -m pip install "requests>=2.0.0,<3.0.0"

To install pre-release versions of packages, use the --pre flag:

python3 -m pip install --pre requests

py -m pip install --pre requests

Install extras#

Some packages have optional extras. You can tell pip to install these by specifying the extra in brackets:

python3 -m pip install 'requests[security]'

py -m pip install "requests[security]"

Install a package from source#

pip can install a package directly from its source code. For example, to install the source code in the google-auth directory:

cd google-auth
python3 -m pip install .

cd google-auth
py -m pip install .

Additionally, pip can install packages from source in development mode, meaning that changes to the source directory will immediately affect the installed package without needing to re-install:

python3 -m pip install --editable .

py -m pip install --editable .

Install from version control systems#

pip can install packages directly from their version control system. For example, you can install directly from a git repository:

google-auth @ git+https://github.com/GoogleCloudPlatform/google-auth-library-python.git

For more information on supported version control systems and syntax, see pip’s documentation on VCS Support.

Install from local archives#

If you have a local copy of a Distribution Package’s archive (a zip, wheel, or tar file) you can install it directly with pip:

python3 -m pip install requests-2.18.4.tar.gz

py -m pip install requests-2.18.4.tar.gz

If you have a directory containing archives of multiple packages, you can tell pip to look for packages there and not to use the Python Package Index (PyPI) at all:

python3 -m pip install --no-index --find-links=/local/dir/ requests

py -m pip install --no-index --find-links=/local/dir/ requests

This is useful if you are installing packages on a system with limited connectivity or if you want to strictly control the origin of distribution packages.

Install from other package indexes#

If you want to download packages from a different index than the Python Package Index (PyPI), you can use the --index-url flag:

python3 -m pip install --index-url http://index.example.com/simple/ SomeProject

py -m pip install --index-url http://index.example.com/simple/ SomeProject

If you want to allow packages from both the Python Package Index (PyPI) and a separate index, you can use the --extra-index-url flag instead:

python3 -m pip install --extra-index-url http://index.example.com/simple/ SomeProject

py -m pip install --extra-index-url http://index.example.com/simple/ SomeProject

Upgrading packages#

pip can upgrade packages in-place using the --upgrade flag. For example, to install the latest version of requests and all of its dependencies:

python3 -m pip install --upgrade requests

py -m pip install --upgrade requests

Using a requirements file#

Instead of installing packages individually, pip allows you to declare all dependencies in a Requirements File. For example you could create a requirements.txt file containing:

requests==2.18.4
google-auth==1.1.0

And tell pip to install all of the packages in this file using the -r flag:

python3 -m pip install -r requirements.txt

py -m pip install -r requirements.txt

Freezing dependencies#

Pip can export a list of all installed packages and their versions using the freeze command:

python3 -m pip freeze

py -m pip freeze

Which will output a list of package specifiers such as:

cachetools==2.0.1
certifi==2017.7.27.1
chardet==3.0.4
google-auth==1.1.1
idna==2.6
pyasn1==0.3.6
pyasn1-modules==0.1.4
requests==2.18.4
rsa==3.4.2
six==1.11.0
urllib3==1.22

The pip freeze command is useful for creating Requirements Files that can re-create the exact versions of all packages installed in an environment.