pypaste

A command line tool for formatting python code enabling trouble free pasting into a python interpreter.

When you paste code into a python terminal, particularly code containing classes, it can complain about unexpected indents. This tool fixes that problem by parsing python code and returning nicely formatted code that will make your interpreter happy.

Neovim setup

The simplest setup is in Neovim since you can just use the iron REPL.

(1) First install the optimized release target. If you don't already have rust installed get cargo from here.

cargo install --git https://github.com/peter-fm/pypaste

(make sure ~/.cargo/bin is on your path)

Then add this as a plugin (e.g. ~/.config/nvim/lua/plugins/iron.lua). I'm assuming you're using uv hence the uv run python. But you could just put system python.

return {
  "Vigemus/iron.nvim",
  config = function()
    local iron = require("iron.core")
    local view = require("iron.view")
    local common = require("iron.fts.common")

    --------------------------------------------------------------------
    -- 1. Formatter: run code through `pypaste` before sending to REPL
    --------------------------------------------------------------------
    local function pypaste_formatter(lines, extras)
      local input = table.concat(lines, "\n")
      local out = vim.fn.system({ "pypaste" }, input)

      if vim.v.shell_error ~= 0 then
        vim.notify("pypaste error:\n" .. out, vim.log.levels.ERROR)
        return lines
      end

      -- Split output to lines (pypaste adds a newline itself)
      local out_lines = vim.split(out, "\n", { plain = true })
      if out_lines[#out_lines] == "" then
        table.remove(out_lines)
      end

      -- Properly wrap with Iron's bracketed paste for Python
      return common.bracketed_paste_python(out_lines, extras)
    end

    --------------------------------------------------------------------
    -- 2. Iron setup
    --------------------------------------------------------------------
    iron.setup({
      config = {
        repl_definition = {
          python = {
            command = { "uv", "run", "python" },
            format = pypaste_formatter,
            env = { PYTHON_BASIC_REPL = "1" },
          },
        },
        repl_open_cmd = view.bottom(40),
      },
      keymaps = {
        toggle_repl = "<leader>rr",
        send_line = "<leader>rl",
        visual_send = "<leader>rs",
        send_file = "<leader>rf",
        clear = "<leader>rc",
      },
    })

    --------------------------------------------------------------------
    -- 3. Fallback REPL starter (if filetype is empty)
    --------------------------------------------------------------------
    vim.keymap.set("n", "<leader>rr", function()
      local ft = (vim.bo.filetype ~= "" and vim.bo.filetype) or "python"
      require("iron.core").repl_for(ft)
    end, { desc = "Start REPL" })

    --------------------------------------------------------------------
    -- 4. Easier terminal navigation + escape
    --------------------------------------------------------------------
    vim.keymap.set("t", "<Esc>", [[<C-\><C-n>]], { noremap = true, silent = true })
    vim.keymap.set("t", "<C-h>", [[<C-\><C-n><C-w>h]], { noremap = true, silent = true })
    vim.keymap.set("t", "<C-j>", [[<C-\><C-n><C-w>j]], { noremap = true, silent = true })
    vim.keymap.set("t", "<C-k>", [[<C-\><C-n><C-w>k]], { noremap = true, silent = true })
    vim.keymap.set("t", "<C-l>", [[<C-\><C-n><C-w>l]], { noremap = true, silent = true })
  end,
}

Keyboard shortcuts

Action	Keys	Result
Start REPL	Space r r	Opens uv run python split
Send current line	Space r l	Runs through pypaste, sends
Send visual selection	Space r s	Same (via pypaste)
Send entire file	Space r f	Same
Clear REPL	Space r c	Clears REPL screen
Select line	x	Start visual line mode
Expand selection	press x again	Add another line
Shrink selection	X	Remove a line
Move between splits	<C-h/j/k/l>	Works even from inside REPL
Exit REPL typing mode	<Esc>	Easy escape

Helix example

The following is an example using Helix. For more information about installing helix see Installing Helix

Suppose you have a uv python project which has a .venv python environment in your current working directory.

1. Add the following line to your ~/.bashrc, ~/.bash_profile or ~/.zshrc file. (You'll need tmux if you don't already have it installed.)

alias hxpython='tmux split-window -v; tmux rename-window helix-target; tmux send-keys -t helix-target ". ./.venv/bin/activate" C-m;tmux send-keys -t helix-target "python" C-m; tmux select-pane -t 0; activate;'

You will need to refresh your session.

source ~/.bashrc

The hxpython alias creates a python prompt using the virtual environment of the directory you are in. (You'll need to replace the . ./.venv/bin/activate part with conda activate <environment-name> if you use anaconda).

2. Build the optimized release target. If you don't already have rust installed get cargo from here.

cargo install --git https://github.com/peter-fm/pypaste

(make sure ~/.cargo/bin is on your path)

3. Create a helix keyboard shortcut by adding the following to your ~/.config/helix/config.toml file

[keys.normal."\\"]
space = [":pipe-to pypaste -t helix-target:0 -b 900 -d 10" ]

How to use it

Using your favorite terminal (I use ghostty).

1. Start a tmux session > tmux
2. Start your ide! > hypython
3. In the top pane open a python file > hx script.py
4. To send lines from the file to your python REPL select them (e.g. with x) then type \ + space and the code will be sent to your REPL having been correctly formatted by pypaste! (Note you must be in normal mode so press ; first to get back to normal mode if selecting via visual mode).

macOS Issues

In macOS, the above works for small amounts of code but sometimes you can face some weird buffer overflow issues if trying to send a large amount of code in one go. To overcome this you can use pypaste to break the code into smaller chunks and send them directly to the tmux target. For this you can specify the target (-t), the buffer size in bytes (-b) and the delay between chunks in milliseconds (-d). Below is an example of sending the code in 1024 byte chunks with a small 10 millisecond delay between chunks. You may need to try different values until it works.

[keys.normal."\\"]
space = [":pipe-to pypaste -t helix-target:0 -b 1024 -d 10" ]

If piping is causing you issues as well, you can avoid it altogether by using the clipboard mode via the -c flag and changing the shortcut as follows:

[keys.normal."\\"]
space = [":clipboard-yank", ":run-shell-command pypaste -t helix-target:0 -b 1024 -d 10 -c" ]

See pypaste -help for more information.