• current settings and what they do
  • how a developer can add their own
  • how to hide built in settings from a user

Built In Settings

cmd2 has a number of built in settings, which a developer can set a default value, and which users can modify to change the behavior of the application.


Setting App.timing to True outputs timing data after every application command is executed. The user can set this parameter during application execution. (See Other user-settable parameters)


If True, each command the user issues will be repeated to the screen before it is executed. This is particularly useful when running scripts.


Setting App.debug to True will produce detailed error stacks whenever the application generates an error. The user can set this parameter during application execution. (See Other user-settable parameters)

Other user-settable parameters

A list of all user-settable parameters, with brief comments, is viewable from within a running application with:

(Cmd) set --long
allow_ansi: Terminal           # Allow ANSI escape sequences in output (valid values: Terminal, Always, Never)
continuation_prompt: >         # On 2nd+ line of input
debug: False                   # Show full error stack on error
echo: False                    # Echo command issued into output
editor: vim                    # Program used by ``edit``
feedback_to_output: False      # include nonessentials in `|`, `>` results
locals_in_py: False            # Allow access to your application in py via self
prompt: (Cmd)                  # The prompt issued to solicit input
quiet: False                   # Don't print nonessential feedback
timing: False                  # Report execution times

Any of these user-settable parameters can be set while running your app with the set command like so:

set allow_ansi Never

Create New Settings

Your application can define user-settable parameters which your code can reference. First create a class attribute with the default value. Then update the settable dictionary with your setting name and a short description before you initialize the superclass. Here’s an example, from examples/

#!/usr/bin/env python
# coding=utf-8
A sample application for cmd2 demonstrating customized environment parameters
import cmd2

class EnvironmentApp(cmd2.Cmd):
    """ Example cmd2 application. """

    degrees_c = 22
    sunny = False

    def __init__(self):
        self.settable.update({'degrees_c': 'Temperature in Celsius'})
        self.settable.update({'sunny': 'Is it sunny outside?'})

    def do_sunbathe(self, arg):
        if self.degrees_c < 20:
            result = "It's {} C - are you a penguin?".format(self.degrees_c)
        elif not self.sunny:
            result = 'Too dim.'
            result = 'UV is bad for your skin.'

    def _onchange_degrees_c(self, old, new):
        # if it's over 40C, it's gotta be sunny, right?
        if new > 40:
            self.sunny = True

if __name__ == '__main__':
    import sys
    c = EnvironmentApp()

If you want to be notified when a setting changes (as we do above), then define a method _onchange_{setting}(). This method will be called after the user changes a setting, and will receive both the old value and the new value.

(Cmd) set --long | grep sunny
sunny: False                # Is it sunny outside?
(Cmd) set --long | grep degrees
degrees_c: 22               # Temperature in Celsius
(Cmd) sunbathe
Too dim.
(Cmd) set degrees_c 41
degrees_c - was: 22
now: 41
(Cmd) set sunny
sunny: True
(Cmd) sunbathe
UV is bad for your skin.
(Cmd) set degrees_c 13
degrees_c - was: 41
now: 13
(Cmd) sunbathe
It's 13 C - are you a penguin?