68 lines
4.8 KiB
Markdown
68 lines
4.8 KiB
Markdown
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---
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title: Installing and Using Python 3
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---
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## Installing Python 3
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You can download Python from this official <a href='https://www.python.org/downloads/' target='_blank' rel='nofollow'>link</a>. Based on your OS (Windows or Linux or OSX), you might want to install Python 3 following <a href='http://docs.python-guide.org/en/latest/starting/installation/' target='_blank' rel='nofollow'>these instructions</a>.
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## Using Virtual Environments
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It is always a great idea to <a href='https://en.wikipedia.org/wiki/Sandbox_(computer_security)' target='_blank' rel='nofollow'>sandbox</a> your Python installation; and keeping it separate from your _System Python_. The _System Python_ is the path to Python interpreter, which is used by other modules installed along with your OS.
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It's **not safe** to install Python Web-frameworks or libraries directly using _System Python_. Instead, you can use <a href='https://virtualenv.readthedocs.org/en/latest/' target='_blank' rel='nofollow'>Virtualenv</a> to create and spawn a separate Python process when you are developing Python applications.
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### Virtualenvwrapper
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The <a href='https://virtualenvwrapper.readthedocs.org/en/latest/' target='_blank' rel='nofollow'>Virtualenvwrapper module</a> makes it easy for you to manage and sandbox multiple Python sandboxed environments in one machine; without corrupting any modules or services written in Python and used by your machine.
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Of course, most cloud hosted development environment such as <a href='https://www.nitrous.io/' target='_blank' rel='nofollow'>Nitrous</a> or <a href='https://c9.io/' target='_blank' rel='nofollow'>Cloud9</a> also comes with these pre-installed and ready for you to get coding! You can quickly pick a box from your dashboard, and start coding after activating a Python 3 environment.
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In <a href='https://c9.io/' target='_blank' rel='nofollow'>Cloud9</a>, you need to select the Django box while creating a new development environment.
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A few shell command examples would follow. If you wish to copy-paste, do note that the `$` sign is a shorthand for the terminal prompt, it's not part of the command. My terminal prompt looks something like this:
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alayek:~/workspace (master) $
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And, an `ls` would look like
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alayek:~/workspace (master) $ ls
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But, while writing the same in this documentation, I would be writing it as
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$ ls
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Getting back to our discussion, you can create a Python 3 interpreter-included sandbox on Cloud9 by running on your cloud terminal:
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$ mkvirtualenv py3 --python=/usr/bin/python3
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You have to run it only once after creating a new box for your project. Once executed, this command would create a new sandboxed virtualenv ready for you to use, named `py3`.
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To view available virtual environments, you can use
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$ workon
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To activate `py3`, you can use the `workon` command with the name of the environment:
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$ workon py3
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All three terminal commands above would also work on local Linux machines or OSX machines. These are <a href='https://virtualenvwrapper.readthedocs.org/en/latest/#introduction' target='_blank' rel='nofollow'>virtualenvwrapper</a> commands; so if you are planning on using them, make sure you have this module installed and added to `PATH` variable.
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If you are inside a virtual environment; you can easily find that out by checking your terminal prompt. The environment name would be clearly shown in your terminal prompt.
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For instance, when I am inside the `py3` environment; I would be seeing this as my terminal prompt:
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(py3)alayek:~/workspace (master) $
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Notice the `(py3)` in braces! If for some reason, you are not seeing this, even if you are inside a virtual env; you can try doing one of the things <a href='http://stackoverflow.com/questions/1871549/python-determine-if-running-inside-virtualenv' target='_blank' rel='nofollow'>mentioned here</a>.
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To get out of a virtual environment; or to deactivate one - use the command
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$ deactivate
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Again, this works only with virtualenvwrapper module.
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### Pipenv
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An alternative to using virtualenvwrapper is [Pipenv](https://docs.pipenv.org/). It automatically creates virtual environments for your projects, and maintains a `Pipfile` which contains the dependencies. Using Pipenv means you no longer need to use pip and virtualenv separately, or manage your own `requirements.txt` file. For those familiar with JavaScript, Pipenv is similar to using a packaging tool like `npm`.
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To get started with Pipenv, you can follow this very detailed [guide](https://docs.pipenv.org/install.html#installing-pipenv). Pipenv makes it easy to [specify which version of Python](https://docs.pipenv.org/basics.html#specifying-versions-of-python) you wish to use for each project, [import](https://docs.pipenv.org/basics.html#importing-from-requirements-txt) from an existing `requirements.txt` file and [graph](https://docs.pipenv.org/#pipenv-graph) your dependencies.
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