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Lesson 4-07 – Intro to AutoLISP

πŸ€– Lesson 4-07: Intro to AutoLISP

Automate tasks in AutoCAD using the built-in AutoLISP programming language.


πŸ“š What You’ll Learn

By the end of this lesson, you’ll be able to:

  • Understand what AutoLISP is and how it integrates with AutoCAD
  • Write and load basic AutoLISP scripts
  • Automate repetitive drawing tasks
  • Use AutoLISP to create custom commands and improve productivity

🧠 Why It Matters

AutoLISP is a powerful scripting language tailored for AutoCAD. With just a few lines of code, you can automate routine actions, create custom tools, and streamline your workflow. It’s especially useful for teams working on complex drawings or those needing custom functionality not found in default commands.


πŸ› οΈ Tools You’ll Use

Tool / FeatureDescription
Visual LISP EditorAutoCAD’s built-in environment for writing and testing AutoLISP
LOAD or APPLOADLoad external LISP files into the current session
.LSP filesAutoLISP script files
DEFUN, COMMAND, SETQCore AutoLISP functions for defining and executing logic

🧭 Lesson Structure

1️⃣ What is AutoLISP?

  • Brief history of LISP in AutoCAD
  • Difference between AutoLISP, Visual LISP, and other scripting tools
  • Common use cases (e.g., drawing automation, custom commands)

2️⃣ Writing Your First Script

  • Open the Visual LISP Editor
  • Create a new .LSP file
  • Example: A simple script that draws a line between two points
(defun c:drawline ( / pt1 pt2 )
(setq pt1 (getpoint "\nSpecify first point: "))
(setq pt2 (getpoint "\nSpecify second point: "))
(command "LINE" pt1 pt2 "")
)

3️⃣ Loading and Running Scripts

  • Save your .LSP file
  • Use the APPLOAD command to load your script
  • Type the custom command (e.g., DRAWLINE) in the command line to run it

4️⃣ Exploring Basic Syntax

  • Variables with SETQ
  • Functions with DEFUN
  • User input with GETPOINT, GETSTRING, GETREAL
  • Calling AutoCAD commands with COMMAND

5️⃣ Adding Logic and Conditions

  • Use IF statements for conditional logic
  • Example: Check if a point exists before drawing
(if pt1
(command "CIRCLE" pt1 "10")
)

6️⃣ Organizing Your Code

  • Use comments ; to document
  • Indent for readability
  • Break tasks into smaller functions

βœ… Lesson Checklist

TaskCompleted
Created and saved a .LSP file☐
Wrote a basic AutoLISP function using DEFUN☐
Loaded the script using APPLOAD☐
Successfully ran the custom command☐
Used user input functions like GETPOINT☐

πŸ“Œ Quick Tips

TipWhy It Helps
Prefix custom commands with C: (e.g., c:hello)So they’re callable from the AutoCAD command line
Use PRINC at the end of a functionPrevents extra output in the command line
Always comment your codeMakes scripts easier to maintain and reuse
Save your scripts in a dedicated folderHelps organize reusable tools

🧩 Real-World Applications

ScenarioAutoLISP Benefit
Batch drawing editsApply changes across hundreds of drawings automatically
Custom workflowsCreate commands tailored to your team’s needs
Automation for repetitive tasksDraw elements like blocks, layers, or text without effort
Data entry simplificationPrompt users for consistent input via scripts

πŸ“ Files and Resources

File / ResourceDescription
intro_drawline.lspExample file for creating a custom line command
autolisp_cheatsheet.pdfHandy reference for basic functions and syntax
automation_examples.zipSeveral small scripts demonstrating practical use cases

πŸ“– Review Table

Function / CommandDescriptionExample
DEFUNDefines a function(defun c:hello () … )
SETQAssigns a value to a variable(setq pt1 (getpoint))
COMMANDRuns AutoCAD commands via script(command "LINE" pt1 pt2 "")
GETPOINT, GETREALPrompts user for input(getreal "\nEnter radius: ")