pyvim

A Vi clone in Python.

It's a bit experimental, but it's certainly usable.

Issues, questions, wishes, comments, feedback, remarks? Please create a GitHub issue, I appreciate it.

Installation

pip install pyvim

The good things

The editor is written completely in Python. (There are no C extensions). This makes development a lot faster. It's easy to prototype and integrate new features.

We have already many nice things, for instance:

Syntax highlighting of files, using the Pygments lexers.
Horizontal and vertical splits, as well as tab pages. (Similar to Vim.)
All of the functionality of prompt_toolkit. This includes a lot of Vi key bindings, it's platform independent and runs on every Python version from python 2.6 up to 3.4. It also runs on Pypy with a noticable performance boost.
Several :set ... commands have been implemented, like incsearch, number, ignorecase, wildmenu, expandtab, hlsearch, ruler, paste and tabstop.
Other working commands: vsplit, tabnew, only, badd, and many others.
For Python source code, auto completion uses the amazing Jedi library, and code checking in done (asynchronously) through Pyflakes.
Colorschemes can be changed at runtime.

Further, when the project develops, it should also become possible to write extensions in Python, and use Python as a scripting language. (Instead of vimscript, for instance.)

We can also do some cool stuff. Like for instance running the editor on the Python asyncio event loop and having other coroutines interact with the editor.

Some more screenshots

Editing its own source code:

Window layouts (horizontal and vertical splits + tab pages.)

Pyflakes for Python code checking and Jedi for autocompletion:

Other colorschemes:

Chinese input (double width characters):

Configuring pyvim

It is possible to create a .pyvimrc file for a custom configuration. Have a look at this example: pyvimrc

Limitations

Compared to Vi Improved, Pyvim is still less powerful in many aspects.

prompt_toolkit does not (or not yet) allow buffers to have an individual cursor when buffers are opened in several windows. Currently, this results in some unexpected behaviour, when a file is displayed in two windows at the same time. (The cursor could be displayed in the wrong window and other windows will sometimes scroll along when the cursor moves.) This has to be fixed in the future.
The data structure for a buffer is extremely simple. (Right now, it's just a Python string, and an integer for the cursor position.) This works extremely well for development and quickly prototyping of new features, but it comes with a performance penalty. Depending on the system, when a file has above a thousand lines and syntax highlighting is enabled, editing will become noticable slower. (The bottleneck is probably the BufferControl code, which on every key press tries to reflow the text and calls pygments for highlighting. And this is Python code looping through single characters.)
A lot of nice Vim features, like line folding, macros, etcetera are not yet implemented.
Windows support is not that nice. It works, but could be improved. (I think most Windows users are not that interested in this project, but prove me wrong.)

Roadmap

There is no roadmap. I mostly implement the stuff which I need or interests me, or which gives me the opportunity to learn. But feel free to create a GitHub issue to request a new feature. Pull requests are also welcome. (Maybe create an issue first to discuss it, if you're unsure whether I'll merge it.)

Maybe some day we will have a better data structure (Rope), that makes it possible to open really large files. (With good algorithms, Python does not have to be slower than C code.)

Maybe we will also have line folding and probably block editing. Maybe some day we will have a built-in Python debugger or mouse support. We'll see. :)

Why did I create Pyvim?

There are several reasons.

The main reason is maybe because it was a small step after I created the Python prompt-toolkit library. That is a library which is actually only a simply pure Python readline replacement, but with some nice additions like syntax highlighting and multiline editing. It was never intended to be a toolkit for full-screen terminal applications, but at some point I realised that everything we need for an editor was in there and I liked to challenge its design. So, I started an editor and the first proof of concept was literally just a few hundred lines of code, but it was already a working editor.

The creation of pyvim will make sure that we have a solid architecture for prompt-toolkit, but it also aims to demonstrate the flexibility of the library. When it makes sense, features of pyvim will move back to prompt-toolkit, which in turn also results in a better Python REPL. (see ptpython, an alternative REPL.)

Above all, it is really fun to create an editor.

Q & A:

Q: Do you use curses?
A: No, it uses only prompt-toolkit.
Q: Why Python?
A: The only alternative would be Haskell, but I still have to learn that.

Thanks

To Vi Improved, by Bram Moolenaar. For the insparation.
To Jedi, pyflakes and the docopt Python libraries.
To the Python wcwidth port of Jeff Quast for support of double width characters.
To Guido van Rossum, for creating Python.

ralston/pyvim