# Python virtualenv `virtualenv` is a tool to create isolated Python environments. You can read more about it in the [Virtualenv documentation](https://virtualenv.pypa.io/en/stable/). This article provides a quick summary to help you set up and use a virtual environment. ## A Note About Python 3.6 and Ubuntu 16.04 LTS If you’re running Ubuntu 16.04 LTS (or and earlier version), Python 3.5 is likely installed by default. *Don’t remove it!* To get Python 3.6, follow the instructions in this section. ### Add the PPA Run the following command to add the Python 3.6 PPA. ``` sudo add-apt-repository ppa:jonathonf/python-3.6 ``` ### Check for Updates and Install Check for updates and install Python 3.6 via the following commands. ``` sudo apt-get update sudo apt-get install python3.6 ``` Now you have three Python version, use `python` to run version 2.7, `python3` for version 3.5, and `python3.6` for version 3.6. For more information on this subject, check out Ji m’s article [How to Install Python 3.6.1 in Ubuntu 16.04 LTS](http://ubuntuhandbook.org/index.php/2017/07/install-python-3-6-1-in-ubuntu-16-04-lts/). ## Create a Virtual Python Environment `cd` to your project directory and run `virtualenv` to create the new virtual environment. The following commands will create a new virtual environment under my-project/my-venv. ``` cd my-project virtualenv --python python3.6 venv ``` ## Activate the Environment Now that we have a virtual environment, we need to activate it. ``` source venv/bin/activate ``` After you activate the environment, your command prompt will be modified to reflect the change. ## Add Libraries and Create a *requirements.txt* File After you activate the virtual environment, you can add packages to it using `pip`. You can also create a description of your dependencies using `pip`. The following command creates a file called `requirements.txt` that enumerates the installed packages. ``` pip freeze > requirements.txt ``` This file can then be used by collaborators to update virtual environments using the following command. ``` pip install -r requirements.txt ``` ## Deactivate the Environment To return to normal system settings, use the `deactivate` command. ``` deactivate ``` After you issue this command, you’ll notice that the command prompt returns to normal. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://book.konstantinsecurity.com/readme/pentest/python-virtualenv.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.