python -m venv tutorial-env
This will create the tutorial-env directory if it doesn’t exist,
and also create directories inside it containing a copy of the Python
interpreter and various supporting files.
A common directory location for a virtual environment is .venv.
This name keeps the directory typically hidden in your shell and thus
out of the way while giving it a name that explains why the directory
exists. It also prevents clashing with .env environment variable
definition files that some tooling supports.
Once you’ve created a virtual environment, you may activate it.
On Windows, run:
tutorial-env\Scripts\activate
On Unix or MacOS, run:
source tutorial-env/bin/activate
(This script is written for the bash shell. If you use the
csh or fish shells, there are alternate
activate.csh and activate.fish scripts you should use
instead.)
Activating the virtual environment will change your shell’s prompt to show what
virtual environment you’re using, and modify the environment so that running
python will get you that particular version and installation of Python.
For example:
$ source ~/envs/tutorial-env/bin/activate
(tutorial-env) $ python
Python 3.5.1 (default, May 6 2016, 10:59:36)
>>> import sys
>>> sys.path
['', '/usr/local/lib/python35.zip', ...,
'~/envs/tutorial-env/lib/python3.5/site-packages']
To deactivate a virtual environment, type:
deactivate
into the terminal.
12.3. Managing Packages with pip
You can install, upgrade, and remove packages using a program called
pip. By default pip will install packages from the Python
Package Index. You can browse the Python
Package Index by going to it in your web browser.
pip has a number of subcommands: “install”, “uninstall”,
“freeze”, etc. (Consult the Installing Python Modules guide for
complete documentation for pip.)
You can install the latest version of a package by specifying a package’s name:
(tutorial-env) $ python -m pip install novas
Collecting novas
Downloading novas-3.1.1.3.tar.gz (136kB)
Installing collected packages: novas
Running setup.py install for novas
Successfully installed novas-3.1.1.3
You can also install a specific version of a package by giving the
package name followed by == and the version number:
(tutorial-env) $ python -m pip install requests==2.6.0
Collecting requests==2.6.0
Using cached requests-2.6.0-py2.py3-none-any.whl
Installing collected packages: requests
Successfully installed requests-2.6.0
If you re-run this command, pip will notice that the requested
version is already installed and do nothing. You can supply a
different version number to get that version, or you can run python
-m pip install --upgrade to upgrade the package to the latest version:
(tutorial-env) $ python -m pip install --upgrade requests
Collecting requests
Installing collected packages: requests
Found existing installation: requests 2.6.0
Uninstalling requests-2.6.0:
Successfully uninstalled requests-2.6.0
Successfully installed requests-2.7.0
python -m pip uninstall followed by one or more package names will
remove the packages from the virtual environment.
python -m pip show will display information about a particular package:
(tutorial-env) $ python -m pip show requests
Metadata-Version: 2.0
Name: requests
Version: 2.7.0
Summary: Python HTTP for Humans.
Home-page: http://python-requests.org
Author: Kenneth Reitz
Author-email: [email protected]
License: Apache 2.0
Location: /Users/akuchling/envs/tutorial-env/lib/python3.4/site-packages
Requires:
python -m pip list will display all of the packages installed in
the virtual environment:
(tutorial-env) $ python -m pip list
novas (3.1.1.3)
numpy (1.9.2)
pip (7.0.3)
requests (2.7.0)
setuptools (16.0)
python -m pip freeze will produce a similar list of the installed packages,
but the output uses the format that python -m pip install expects.
A common convention is to put this list in a requirements.txt file:
(tutorial-env) $ python -m pip freeze > requirements.txt
(tutorial-env) $ cat requirements.txt
novas==3.1.1.3
numpy==1.9.2
requests==2.7.0
The requirements.txt can then be committed to version control and
shipped as part of an application. Users can then install all the
necessary packages with install -r:
(tutorial-env) $ python -m pip install -r requirements.txt
Collecting novas==3.1.1.3 (from -r requirements.txt (line 1))
Collecting numpy==1.9.2 (from -r requirements.txt (line 2))
Collecting requests==2.7.0 (from -r requirements.txt (line 3))
Installing collected packages: novas, numpy, requests
Running setup.py install for novas
Successfully installed novas-3.1.1.3 numpy-1.9.2 requests-2.7.0
pip has many more options. Consult the Installing Python Modules
guide for complete documentation for pip. When you’ve written
a package and want to make it available on the Python Package Index,
consult the Python packaging user guide.
12. Virtual Environments and Packages
