Setting up a Python REPL in Sublime Text using Terminus

Default (Windows).sublime-keymap

[
    // Place the bindings in your user Key bindings for whatever platform you're
    // on (also, change the keys as appropriate for your use).

    // Send a newline to the Terminus Python REPL, if it's open
    { "keys": ["shift+ctrl+enter"], "command": "terminus_send_string",
      "args": {"string": "\n", "tag": "python-repl"},
      "context": [
          { "key": "terminus_tag.exists", "operand": "python-repl" },
          { "key": "selector", "operator": "equal", "operand": "source.python" },
      ],
    },

    // Open a Python REPL using a Terminus buid if it's not already running.
    { "keys": ["ctrl+enter"], "command": "build",
      "args": {
          "build_system": "Packages/User/PythonREPL.sublime-build",
          "variant": "",
      },
      "context": [
          { "key": "terminus_tag.notexists", "operand": "python-repl" },
          { "key": "selector", "operator": "equal", "operand": "source.python" },
      ],
    },

    // Send the current selection or file content to the Terminus Python REPL,
    // if it exists.
    // 
    // You could also augment this by having different keys depending on if
    // there is selected text or not, or constrain the number of selections,
    // etc.
    { "keys": ["ctrl+enter"], "command": "send_selection_to_terminus",
      "args": {"tag": "python-repl"},
      "context": [
          { "key": "terminus_tag.exists", "operand": "python-repl" },
          { "key": "selector", "operator": "equal", "operand": "source.python" },
      ],
    },
]

PythonREPL.sublime-build

{
    "target": "terminus_open",
    "title": "Python REPL",
    "tag": "python-repl",
    "auto_close": false,

    "shell_cmd": "python -u -i \"$file\"",
    "file_regex": "^[ ]*File \"(...*?)\", line ([0-9]*)",
    "selector": "source.python",

    "post_window_hooks": [
        ["carry_file_to_pane", {"direction": "right"}]
    ],

    "env": {"PYTHONIOENCODING": "utf-8"},
}

terminus_repl.py

import sublime
import sublime_plugin


def _terminus_view(window, tagName):
    window = window or sublime.active_window()
    for view in window.views():
        if view.settings().get("terminus_view.tag") == tagName:
            return view

    return None


class SendSelectionToTerminusCommand(sublime_plugin.WindowCommand):
    def run(self, tag=None, visible_only=False):
        view = self.window.active_view()
        if view == None:
            return

        if any(sel.empty() for sel in view.sel()):
            spans = [sublime.Region(0, len(view))]
        else:
            spans = [sel for sel in view.sel() if not sel.empty()]

        for span in spans:
            self.window.run_command("terminus_send_string", {
                "string": view.substr(span),
                "tag": tag,
                "visible_only": visible_only
                })


class SampleREPLListener(sublime_plugin.EventListener):
    def on_query_context(self, view, key, operator, operand, match_all):
        if key == "terminus_tag.exists" or key == "terminus_tag.notexists":
            view = _terminus_view(view.window(), operand)
            return view != None if key == "terminus_tag.exists" else view == None

        return None

These sample files show how to use the Terminus package for Sublime Text to create a custom Python REPL environment without having to also install SublimeREPL. This is demonstrated in my video on setting up a REPL using Terminus.