Calico: Getting Started

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Getting started with Calico. This document describes how to begin using the Calico scripting environment.


Calico is an environment for scripting. It is composed of three main components:

  • Interactive Scripting Language Shell (like Ruby, Python and Scheme)
  • Scripting Editor (files of scripts)
  • Modules for doing things (like robotics and graphics)

Calico is designed so that you can swap out any component, and the other two components can remain the same.

First, you should have already installed Calico at the Calico Download page.


Normally, you can just double-click on the StartCalico icon in Windows, Mac, and Linux.

As a convenience, you might want to associate ".py" files with StartCalico, so that when you double-click a file, it opens it in Calico. Otherwise, you will need to start Calico, and then use menu -> File -> Open.

You can also start Calico up by running the ./StartCalico (Linux and Mac OSX) and StartCalico.bat (Windows) from the command console (also called terminal). You can pass a number of "flags" to Calico. Here we pass the --help flag to see what all of the options are:

C:\Users\dblank\Calico>StartCalico.bat --help

Loading Calico version 2.4.2...

Calico Project, version 2.4.2 on Unix
  Using Mono runtime version (Debian
Start calico with the following options:
  StartCalico                    Standard GUI
  StartCalico FILENAME:LINE ...  Edits FILENAMEs, positioned on LINEs
  StartCalico --lang=LANGUAGE    Sets default language (python, etc.)
  StartCalico --exec FILENAMEs   Run FILENAMEs
  StartCalico --repl FILENAMEs   Run FILENAMEs and starts read-eval-print loop
  StartCalico   --graphics       Run with graphics (with --exec or --repl)
  StartCalico   --noquit         Don't quit after executing file with --exec
  StartCalico --nomodules        Does not load the modules from modules/*.dll
  StartCalico --version          Displays the version number (2.4.2)
  StartCalico --verbose          Displays detailed information (for debugging)
  StartCalico --debug            Calico output goes to console rather than GUI
  StartCalico --debug-handler    Calico will not catch system errors
  StartCalico --reset            Resets config settings to factory defaults
  StartCalico --help             Displays this message

There are three main modes of operation:

  1. with the standard Calico GUI
  2. --exec runs code; does not bring up GUI
  3. --repl runs a console read-eval-print loop, after running any programs

Additionally, there is the --graphics flag. By default, Calico assumes that you do not want to initiate and run the graphical event loop. --graphics only makes sense when you are using --exec or --repl.

If you have a graphical program, and run without the Calico GUI, then you might want to have your graphical windows exit Calico. You can do that with something like:

from Graphics import Window
import System
win = Window()
win.DeleteEvent += lambda obj, event: System.Environment.Exit(0)


To edit a program:

StartCalico myprog.rb

To edit a program, starting on line 200:

StartCalico myprog.rb:200

To edit a bunch of programs:

StartCalico *.py

This page provides some examples of using Calico.

Calico GUI


Calico is divided into three parts:

  1. Editor
  2. Shell
  3. Output

The Editor allows you to edit files. From the editor, you can select a section of code and press F5 to run part of your script interactively. If you don't have anything high-lighted, pressing F5 will run the entire file.

In the interactive command box, you can enter as much code as you like, ENTER will evaluate the code in the box (you may have to press ENTER twice, if you have a multi-line expression).

Running Scripts

There are 5 widgets involved with running a script. From left to right they are:

  • Stop, stops the program
  • Run, starts the program
  • Speed slider, from (left) fast to single-step (right), with auto-pausing in between
  • Pause
  • Next/Resume step

These are used in the following ways:

  • To start running, with stepper or fast, you press the Run button
  • If the slider is far to left (fast) when you press the Run button, it runs regularly (no debugging)
  • If the slider is in the middle, then the debugger will run with an auto-pause on (between 0.1 and 1 second pause per line). You can press the Pause button at any time.
  • If the slider is on the far right, then it is in single-step mode. You can press the Next button to go to next line.
  • You can press the Pause button when slider is in middle, and the program is running
  • You can press the Next/Resume button when slider is in middle (resumes), or if slider is far-right (next)

Example Code

You'll find the example code in Calico: menu -> File -> Examples -> pick your language.

Keyboard Commands


General shortcuts in the shell:

  • Control + Enter: newline (does not evaluate)
  • TAB: after some text will do command completion
  • Up arrow: previous command
  • Down arrow: next command
  • Control+Up arrow: take the current command, and put it on the bottom of the previous command
  • Control+Down arrow: take the current command, and put it on the top of the next command
  • F5: evaluate the text in the command entry box
  • Block select: Control + Alt + mouse drag
  • Run the script in the command area, if a one-liner: Return key
  • Run the script in the command area, if a multi-liner: Return key on line with only white-space
  • Enter a blank line in command area: Enter key
  • Drag text to command area, then F5
  • Stop processing: Escape key

Selection shortcuts in the shell:

  • Select: Shift + arrow keys; Shift + Control + arrow keys; left-click and mouse drag; double-, triple- left-mouse click
  • Select all: Control + A
  • Block select: Control + Alt + mouse drag

Movement shortcuts in the shell:

  • Move by word: Control + arrow keys
  • To top: control + Home
  • to bottom: control + end
  • Beginning of line: home
  • End of line: end


General shortcuts in the editor:

  • F5: evaluate highlighted text, or the entire file if nothing highlighted
  • Zoom in: Control + mouse wheel forwards
  • Zoom out: Control + mouse wheel backwards
  • Indent block: select and press Tab
  • Unindent block: select and press Shift+Tab
  • Undo: Control + Z
  • Redo: Control + Shift + Z
  • Cut: Control + X
  • Copy: Control + C
  • Paste: Control + V
  • Move block: Control + left mouse drag
  • Auto indent: will automatically indent to the level of the previous line
  • Unindent a line: shift + Tab
  • Indent a line: go to begging of line, press Tab key

Searching Shortcuts in the editor:

  • Control + F: bring up search bar
  • Control + G: find next
  • Control + R: find previous
  • Enter: find next
  • Shift + Enter: find previous
  • Escape: close search bar

Selection shortcuts in the editor:

  • Select: Shift + arrow keys; Shift + Control + arrow keys; left-click and mouse drag; double-, triple- left-mouse click
  • Select all: Control + A
  • Block select: Control + Alt + mouse drag

Movement shortcuts in the editor:

  • Move by word: Control + arrow keys
  • To top: control + Home
  • to bottom: control + end
  • Beginning of line: home
  • End of line: end


Visual cues:

  • Yellow in margin: line has been edited
  • Green in margin: line has been edited and saved
  • Current line has grey background

Example 1: Draw a circle

In these examples we will use Python.

Our goals are:

  1. Import the Graphics library
  2. Create a window
  3. Create a circle, center at (150, 150) (zero is upper lefthand corner, x and y increase as they go away from upperleft hand corner). Make the radius 80 pixels.
  4. Draw the circle in the window

Here is a sample that satisfies our goals:

from Graphics import *
win = Window()
circle = Circle(Point(150, 150), 80)

In the Graphics library, you can substitute a tuple or list for a Point. So, these are equivalent:

from Graphics import *
win = Window()
circle = Circle((150, 150), 80)


from Graphics import *
win = Window()
circle = Circle([150, 150], 80)

Example 2: Move Circle Interactively

Our goals for this example:

  1. Create a window that is 480 x 120, titled "Circles"
  2. Create a circle, as before, and draw it in the window
  3. In a loop, continue forever:
    1. if the mouse is down, make the circle black
    2. else make it white

Here is a short Python program that satisfies the goals:

from Graphics import *
win = Window("Circles", 480, 120)
circle = Circle(getMouseNow(), 80)
while win.isVisible(): = Point(getMouseNow())
    if getMouseState() == "down":
        circle.fill = Color("black")
        circle.fill = Color("white")

Note: This example code does not end, so you need to click the red stop sign in the Shell window.


See Calico Videos for a variety of videos, including some on getting started.