Color Django shell by development environment

I often perform operational tasks such as modifying data or debugging failures using the Django shell. In fact, anything I can't do through the admin or through management commands I use the shell for. The package django-extensions provides a shell on steroids that I much prefer over the built in shell. It allows you to run a custom REPL such as IPython or Ptpython and has autocomplete, command history, automatic model class imports and a myriad of other dev tools. shell_plus is for a Django programmer what a scalpel is for a surgeon.

Most Django sites that have receive some amount of traffic have multiple development environments. Naturally there is always a production environment and usually a staging and (local) development environment. In the past I've fat-fingered and corrupted production data while thinking I was working on the staging environment. To avoid the fiasco I've built tooling to reduce the probability of future fuck-ups.

Using the shell and some Python configuration we can get visual indicators of what environment we're in. I like to mark the production environment in some tone of red to indicate danger and staging in blue to indicate that careless hacking is fine.

Local development

Staging

Production

Installing shell_plus and ptpython

To use a programmable shell we need the following ingredients:

• django-extensions/django-extensions which contains the management command shell_plus and many other great tools
• prompt-toolkit/ptpython a better Python REPL which will power the shell_plus experience. You could use other REPLs such as IPython or BPython, but I prefer ptpython.

Enable django_extensions by adding it to your INSTALLED_APPS

INSTALLED_APPS = (
    ...
    "django_extensions",
    ...
)

By default shell_plus will detect and use an enhanced REPL if one is installed.

Customizing ptpython

Ptpython reads from a configuration file where we can specify custom keybindings and the REPL colorscheme. The default configuration file can be copied from prompt-toolkit/ptpython/blob/master/examples/ptpython_config/config.py.

At the bottom of the configure method we'll add code that detects the current environment and changes the REPL title and colors depending the environment. I use Sentry in nearly all of my projects and filter issues based on the environment. SENTRY_ENVIRONMENT is injected by the deployment tool and we can use that variable to paint the shell distinctly for each environment. I like black for local development, blue for staging and red for production. Additionally we'll make the ptpython toolbar use bold font for for staging and production.

"""
Configuration example for ``ptpython``.
Copy this file to $XDG_CONFIG_HOME/ptpython/config.py
On Linux, this is: ~/.config/ptpython/config.py
"""
import os

from prompt_toolkit.styles import Style

__all__ = ["configure"]


def configure(repl):
    # Default configuration above...

    # Read the environment variable from what we set for Sentry
    environment = os.environ.get("SENTRY_ENVIRONMENT", "local")

    if "prod" in environment:
        custom_colorscheme = {"status-toolbar": "bg:#C70039 #000000 bold"}
        title = "PRODUCTION"
    elif "staging" in environment:
        custom_colorscheme = {"status-toolbar": "bg:#005ca4 #000000 bold"}
        title = "STAGING"
    else:
        custom_colorscheme = {"status-toolbar": "#000000"}
        title = "DEV"

    repl.install_ui_colorscheme("custom", Style.from_dict(custom_colorscheme))
    repl.use_ui_colorscheme("custom")
    repl.title = title

All that's left to do is to start the shell

./manage.py shell_plus

If you're trying out different colors and want to reflect the changes in real-time you can set the variable for the command and copy the configuration file to reflect the changes.

cp ptpython_config.py ~/.config/ptpython/config.py && SENTRY_ENVIRONMENT=production ./manage.py shell_plus

Configuring ptpython for Docker

FROM python:3.10.8

# Install your dependencies here

COPY ptpython_config.py /root/.config/ptpython/config.py

COPY . /app/

CMD ["gunicorn", "-b", "0.0.0.0:80", "config.wsgi"]