Develop Reference

Enviroment variables in pyenv-virtualenv

I have created a virtual environment with pyenv virtualenv 3.5.9 projectname for developing a django project.
How can I set environment variables for my code to use?
I tried to add the environment variable DATABASE_USER in /Users/developer/.pyenv/versions/projectname/bin/activate
like this:
export DATABASE_USER="dbuser"
When I tried to echo $DATABASE_USER an empty string gets printed.
Tried to install zsh-autoenv
And now I can echo $DATABASE_USER and get the value set in the .autoenv.zsh file.
But I can't seem to get the environment variable to be available to my django code:
If I try to os.getenv('DATABASE_USER', '') in the python shell inside the virtualenv, I get ''
What could be wrong? Is the zsh-autoenv variables just available for the zsh shell and not python manage.py shell ?

I was wondering a similar thing, and I stumbled across a reddit thread where someone else had asked the same question, and eventually followed up noting some interesting finds.
As you noticed, pyenv doesn't seem to actually use the bin/activate file. They didn't say what the activation method is, but like you, adding environment variables there yielded no results.
In the end, they wound up installing autoenv, which bills itself as directory-based environments. It allows you to create an .env file in your directory, and when you cd to that directory, it runs the .env file. You can use it for environment variables, or you could add anything else to it.
I noticed on the autoenv page that they say you should probably use direnv instead, as it has better features and is higher quality software. Neither of these are Python or pyenv specific, and if you call your python code from outside of the directory, they may not work. Since you're using pyenv, you're probably running your code from within the directory anyway, so I think there's a good chance either one could work.

PyCharm Virtual Environment Concept - Understanding [duplicate]

I am fairly new to creating Python applications. I have fooling around with some small tutorials and applications using PyCharm and have always created a new project using the Virtualenv environment, ending up with a "venv" folder under my project folder. I have not had any problems with this, but then again I have not done any large projects.
However, I have been wanting to learn Flask want to try to create a new Flask project the proper way. I see in many tutorials that people are creating (and activating) the virtual environment from the (Windows/Linux) Command Line instead even though they are using PyCharm and I was just wondering what the difference is?
When I work on a project in PyCharm, created with Virtualenv, I do not activate the venv before working on it. Is this wrong or is this something that is handled by PyCharm? What if the venv is created from a Command Line? Is it still handled (activated) by PyCharm if working on the project there. And what about the folder structure? Is this affected by how the virtual environment is created? Is there somewhere I can find some "best practices" for the setup / folder structure when creating Flask project within a Virtual Environment?

PyCharm activates the VirtualEnv for you if it is configured to use one and told where it is (more specifically, where the respective Python binary in the VirtualEnv is).
There's no real difference between manually created VirtualEnvs and ones created by PyCharm. (Apart from the framework you select to create one in case this is different from what PyCharm is configured with.)
If you want, you can just create one manually and then point PyCharm to it. Either during creation of the project or later using the Settings dialog (see Settings -> Project -> Project Interpreter). It will then treat it no differently and also activate it for you when working inside the IDE.

A virtual environment is pretty much just a folder which stores installed Python packages and isolates them from the rest of your system. This is so you can work on different projects which may all have competing requirements for external packages, without getting into conflicts. "Activating" a virtual environment just sets certain environment variables in your current shell so it'll use packages from this environment. "Activating" an environment never has any impact beyond your current shell. So activating an environment on the command line won't do anything to PyCharm.
PyCharm integrates a Python interpreter to give you lots of extra functionality. You tell PyCharm which interpreter you want to use for your project and it'll figure out what packages it has available, what version it is, and automatically set everything up properly for running your code from PyCharm etc. You can tell PyCharm to use your system's Python interpreter or an existing virtual environment or even use it to create a new environment. You don't need to do anything special beyond just selecting the right interpreter/environment in the project settings.
There's no reason to activate the environment from the command line if you're not going to use it from the command line. Of course, using Flask and running its server from the command line and keeping it running in the background may be useful. Not sure if PyCharm would give you an easy or integrated option to have persistent processes run in the background. You could still select the same virtual environment in PyCharm and use it to run your tests in it directly from PyCharm, use its debugger etc.
I prefer to keep the venv out of the project folder and store all venvs in ~/.virtualenvs/ or such. It declutters the project folder and prevents accidentally checking those files into the version control system.

I was just wondering what the difference is?
There's many tools for creating and using virtual environments and there's no difference between them, the only difference between them is their commands syntax (or the way it interact with users, e.g. for Pycharm you set some settings via GUI).
Is this wrong or is this something that is handled by PyCharm?
There's nothing wrong with it. As long as you have a venv (or .venv) directory in the root of your project and it is executable for any user, Pycharm will use it and it activates this virtual environment for you (without telling you). If Pycharm was not able to do that, (because of trouble in finding venv or activating/executing it!) then it will show you messages to fix its problems and it can't run your project till you fix them.
It's better to create your virtual environment in .venv directory right into the root directory of your project. (It's kind of conventional)
See python virtual environments and configuring pycharm virtualenv as well.

After activate a python virtual environment, typing `python` still get me the version in PATH

I am using windows 7. I have multiple python virtual environments. Say I added venv_1 to system PATH. In the command line, say I activate another venv_2, now the prompt line shows
(venv_2) C:\>
But if I type python here, it still runs the python in venv_1.
Is this the intended behavior?

This is not the intended behaviour, but it probably means you either made a mistake in setting up the virtual environment, or in activating it.
To be sure what version is being run, try running:
where python
Whatever the top item in the resulting list is, will be the copy of Python Windows would start. If you're right and it does actually point to venv_1, then there must be something wrong with the setup in venv_2.
By running set, you should be able to see a list of all environment variables. Check for:
PATH=<long list of directory names, it should have the venv_2\Scripts at the start>
And:
_OLD_VIRTUAL_PATH=<the same list, without that entry>
It's this simple change to the path that causes Windows to find the Python in your virtual environment first, before the one in your other virtual environment, that you added to the global path.
Note that adding the Scripts folder of the one virtual environment probably isn't a good idea, since you'd only want to use that when the corresponding virtual environment is activated and all the environment variables set accordingly.

Python path on windows

I have two installations of Python on a corporate Windows computer. One from the Anaconda distribution:
C:\Users\Me\AppData\Local\Continuum\anaconda3\python3.exe
Another one from a corporate installer:
C:\Users\Me\AppData\Local\Downloaded Apps\WinPython\python-3.4.3\python.exe
If I type "python" in the default "cmd" terminal or in the Git Bash, it says "command not found". Probably for the same reason, Jupyter does not allow me to create a Python 3 notebook. How do I set the paths so that Python is available system-wide? I prefer the Anaconda distribution's Python.
EDIT: Creating a new user variable PYTHONPATH and setting it to C:\Users\Me\AppData\Local\Continuum\anaconda3\ via Windows System Properties does not have an effect.

This answer describes step-by-step an approach that worked for me. However, as eryksun notes in the comment, the additional variable should not be named PYTHONPATH. I renamed it PYTHON, which works.
Strangely, adding the paths directly to the PATH variable did NOT work.

You have to add the path of your installation to the Environment variables.
Simply go to the System Properties / Environment Variables /
From there, create a new system variables and add your python path.

In the system variable section select the Path variable.
Add new variable C:\Users\Me\AppData\Local\Continuum\anaconda3\ as environment variable in your advanced System Settings.
This is from where your system will invoke the python interpreter.
For more details see this answer

Associating a python project with a virtual environment

been searching for this with no success, i don't know if i am missing something but i have a virtualenv already but how do i create a project to associate the virtualenv with, thanks
P.S. Am on windows

I could be wrong here, but I do not believe that a virtualenv is something that is by its very nature something that you associate with a project. When you use a virtualenv, you're basically saying, "I'm taking this Python interpreter, installing what I want on it, and setting it aside from the Python interpreter that the entire computer uses by default." Virtualenv does not have a concept of a Python "project"; it is just a custom version of a Python interpreter that you run code through. There are tools in IDEs like PyCharm that enable you to associate a project with a virtualenv, but those are another layer on top of the base software.
In order to use a virtualenv with a project, you will need to "activate" it every time you wish to use it. The documentation for activating a virtualenv on Windows is found here.
EDIT:
Saw that you had virtualenvwrapper tagged in your post, so I did a bit of hunting on that. It would appear that there is the mkproject command, which creates a project folder and then associates it with a virtualenv interpreter. Documentation on it can be found here.

Requirements:
Virtual Env
Pycharm
Go to Virtual env and type which python
Add remote project interpreter (File > Default Settings > Project Interpreter (cog) add remote)
You'll need to set up your file system so that PyCharm can also open the project.
NOTE:
do not turn off your virtual environment without saving your run configurations that will cause pycharm to see your run configurations as corrupt
There's a button on the top right that reads share enable this and your run configs will be saved to a .idea file and you'll have a lot less issues

If you already have your virtualenv installed you just need to start using it.
Create your projects virtual environment using virtualenv env_name on cmd. To associate a specific version of python with your environment use: virtualenv env_name -p pythonx.x;
Activate your environment by navigating into its Scripts folder and executing activate.
Your terminal now is using your virtual environment, that means every python package you install and the python version you run will be the ones you configured inside your env.
I like to create environments with the names similar to my projects, I always use one environment to each project, that helps keeping track of which packages my specific projects need to run.
If you haven't read much about venvs yet, try googling about requirements.txt along with pip freeze command those are pretty useful to keep track of your project's packages.

I like Pipenv: Python Dev Workflow for Humans to manage environments:
Pipenv is a tool that aims to bring the best of all packaging worlds (bundler, composer, npm, cargo, yarn, etc.) to the Python world. Windows is a first-class citizen, in our world.
It automatically creates and manages a virtualenv for your projects, as well as adds/removes packages from your Pipfile as you install/uninstall packages. It also generates the ever-important Pipfile.lock, which is used to produce deterministic builds.
Pipenv is primarily meant to provide users and developers of applications with an easy method to setup a working environment.