How to install a package inside virtualenv?

Question

I created a virtualenv with the following command.

mkvirtualenv --distribute --system-site-packages "$1"

After starting the virtualenv with workon, I type ipython. It prompts me

WARNING: Attempting to work in a virtualenv. If you encounter problems, please install IPython inside the virtualenv.

When I try to install ipython with the virtualenv, I got the following error message:

pip install ipython
Requirement already satisfied (use --upgrade to upgrade): ipython in /Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages
Cleaning up...

Does anyone know how to install inside the virtualenv?

Answer 1

Sharing what has worked for me in both Ubuntu and Windows. This is for python3. To do for python2, replace "3" with "2":

Ubuntu

pip install virtualenv --user
virtualenv -p python3 /tmp/VIRTUAL
source /tmp/VIRTUAL/bin/activate
which python3

To install any package: pip install package

To get out of the virtual environment: deactivate

To activate again: source /tmp/VIRTUAL/bin/activate

Full explanation here.

Windows

(Assuming you have MiniConda installed and are in the Start Menu > Anaconda > Anaconda Terminal)

conda create -n VIRTUAL python=3  
activate VIRTUAL

To install any package: pip install package or conda install package

To get out of the virtual environment: deactivate

To activate again: activate VIRTUAL

Full explanation here.

Answer 2

To further clarify the other answer here:

Under the current version of virtualenv, the --no-site-packages flag is the default behavior, so you don't need to specify it. However, you are overriding the default by explicitly using the --system-site-packages flag, and that's probably not what you want. The default behavior (without specifying either flag) is to create the virtual environment such that when you are using it, any Python packages installed outside the environment are not accessible. That's typically the right choice because it best isolates the virtual environment from your local computer environment. Python packages installed within the environment will not affect your local computer and vice versa.

Secondly, to use a virtual environment after it's been created, you need to navigate into the virtual environment directory and then run:

bin/activate

What this does is to configure environment variables so that Python packages and any executables in the virtual environment's bin folders will be used before those in the standard locations on your local computer. So, for example, when you type "pip", the version of pip that is inside your virtual environment will run instead of the version of pip on your local machine. This is desirable because pip inside the virtual environment will install packages inside the virtual environment.

The problem you are having is because you are running programs (like ipython) from your local machine, when you instead want to install and run copies of those programs isolated inside your virtual environment. You set this up by creating the environment (without specifying any site-packages flags if you are using the current version), running the activate script mentioned above, then running pip to install any packages you need (which will go inside the environment).

Answer 3

Create your virtualenv with --no-site-packages if you don't want it to be able to use external libraries:

virtualenv --no-site-packages my-virtualenv
. my-virtualenv/bin/activate
pip install ipython

Otherwise, as in your example, it can see a library installed in your system Python environment as satisfying your requested dependency.

Answer 4

I tried here to give an answer, with a complete view and also with some good tips.

So, here are some instructions that could avoid headaches when using Virtual Environments:

• Create a folder for your projects.
• Create your Virtualenv projects inside of this folder.
• After activating the environment of your project, never use "sudo pip install package".
• After finishing your work, always "deactivate" your environment.
• Avoid renaming your project folder.

---

For a better representation of these practices, here's a simulation:

creating a folder for your projects/environments

$ mkdir venv

creating environment

$ cd venv/ 

$ virtualenv google_drive
New python executable in google_drive/bin/python
Installing setuptools, pip...done.

activating environment

$ source google_drive/bin/activate

installing packages

(google_drive) $ pip install PyDrive
Downloading/unpacking PyDrive
Downloading PyDrive-1.3.1-py2-none-any.whl
...
...
...    
Successfully installed PyDrive PyYAML google-api-python-client oauth2client six uritemplate httplib2 pyasn1 rsa pyasn1-modules
Cleaning up...

package available inside the environment

(google_drive) $ python
Python 2.7.6 (default, Oct 26 2016, 20:30:19) 
[GCC 4.8.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>
>>> import pydrive.auth
>>>  
>>> gdrive = pydrive.auth.GoogleAuth()
>>>

deactivate environment

(google_drive) $ deactivate 

$ 

package NOT AVAILABLE outside the environment

$ python
Python 2.7.6 (default, Oct 26 2016, 20:32:10) 
[GCC 4.8.4] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>>
>>> import pydrive.auth
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: No module named pydrive.auth
>>> 

---

Notes:

Why not sudo?

Virtualenv creates a whole new environment for you, defining $PATH and some other variables and settings. When you use sudo pip install package, you are running Virtualenv as root, escaping the whole environment which was created, and then, installing the package on global site-packages, and not inside the project folder where you have a Virtual Environment, although you have activated the environment.

If you rename the folder of your project...

...you'll have to adjust some variables from some files inside the bin directory of your project.

For example:

bin/pip, line 1 (She Bang)

bin/activate, line 42 (VIRTUAL_ENV)

Answer 5

I had the same issue and the --no-site-packages did not work for me. I discovered on this older mailing list archive that you are able to force an installation in the virtualenv using the -U flag for pip, eg pip -U ipython. You may verify this works using the bash command which ipython while in the virtualenv.

source: https://mail.python.org/pipermail/python-list/2010-March/571663.html

Answer 6

For Python 3 :

pip3 install virtualenv

python3 -m venv venv_name

source venv_name/bin/activate  #key step

pip3 install "package-name"