Please code a parametric keychain with extruded text and a hanging loop in OpenSCAD for 3D printing
Sure! Here's an example code for a parametric keychain with extruded text and a hanging loop in OpenSCAD:

```scss
// keychain parameters
keychain_thickness = 3; // overall thickness of keychain
text_thickness = 1; // thickness of extruded text
text_height = 5; // height of extruded text
text_size = 12; // font size of text
loop_radius = 10; // radius of hanging loop
loop_thickness = 1; // thickness of hanging loop
keychain_width = 30; // width of keychain

// create the hanging loop
module hanging_loop() {
  difference() {
    cylinder(r = loop_radius, h = loop_thickness, center = true);
    cylinder(r = loop_radius - loop_thickness, h = loop_thickness + 0.1, center = true);
  }
}

// create the keychain with extruded text and hanging loop
module keychain() {
  difference() {
    // create the keychain shape
    cube([keychain_width, keychain_width, keychain_thickness]);
    // extrude the text and position it on the keychain
    translate([keychain_width/2 - text_size/2, keychain_width/2 - text_size/2, keychain_thickness]) 
    linear_extrude(height = text_height, convexity = 10) 
    text(Hello, World!, size = text_size);
    // position the hanging loop at the top of the keychain
    translate([keychain_width/2, keychain_width/2, keychain_thickness - loop_thickness]) 
    hanging_loop();
  }
}

// generate the keychain
keychain();
```

You can adjust the parameters at the top of the code to customize the keychain to your desired size and text. Once you've made any desired adjustments to the parameters, save the file with a .scad extension and open it in OpenSCAD. Then, click the Compile and Render button to see a preview of the 3D model. Finally, export the model as an STL file and load it into your 3D printing software to print the keychain.