Frequently Asked Questions

Why isn’t VirtualFish written in Python?

Mostly, for the same reasons virtualenvwrapper is.

Does VirtualFish work with Python 3? What about PyPy?

Yes! In fact, you can create Python 3 virtual environments even if your system Python is Python 2, or vice versa, using the --python argument (see the Usage section for full details).

Why does VirtualFish use Virtualenv and not Python’s built-in venv module?

Virtualenv can create both Python 2 and Python 3 virtual environments, whereas Python’s built-in venv module can only create Python 3 virtual environments. That said, since Python 2 is no longer officially supported by the Python Software Foundation, Python 2 support is a very minor consideration when deciding which tool to use. The main reason VirtualFish uses Virtualenv is due to its much faster speed. We have seen Virtualenv create environments in one-fifth the amount of time that the venv module takes to perform the same task.

Why doesn’t VirtualFish use

VirtualFish uses its own internal virtualenv activation code instead of the file that comes with every virtualenv for two main reasons. One is that when VirtualFish was originally written, didn’t actually work. The second reason, which is still valid today, is that tries to modify your fish_prompt function.

Because fish_prompt is a function and not a variable like in most other shells, modifying it programmatically is not trivial, and the way that Virtualenv accomplishes it is more than a little hacky. The benefit of it being a function is that the syntax for customising it is much less terse and cryptic than, say, PS1 on Bash. This is why VirtualFish doesn’t attempt to modify your prompt, and instead tells you how to do it yourself.