PyCharm 与命令行的虚拟环境对比

Question

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?

Answer 1

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.

Answer 2

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.

Answer 3

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, eg 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.