My First Template

Now when the Grasshopper component is written, it is time to write the template and the CPython script. Navigate to where you put the and open it. It can easily be found by in explorer typing:


Python scripts can be opened and edited with a range of editors: Notepad, Notepad++ or Spyder, which comes with the Anaconda installation, is among the simplest.

The top function in is the function we used in the component: pick_template()

def pick_template(template_name, path):
    Writes a template given a template name and path to write it to.

    :param template_name: Template name.
    :param path: Path to save it to.

    template_name = str(template_name)

    if template_name == 'my_first_template':

    elif template_name == 'plot_graph':

        raise NameError('Could not find template: ' + str(template_name))

    return True

pick_template is a convenient way of writing out different templates with the same function. You just need to give the name of the template and a path, where the template should be written. At the moment it is possible to write out two templates. For this tutorial we will only use the first one. When pick_template receives the template_name: "my_first_template", the function my_first_template() will be called. Therefore, we need to create a function called my_first_template()

def my_first_template(path):
    Writes a template.

    :param path: Path to write it to.
    :type path: str
    :return: The file name

    file_name = r'/'
    file = open(path + file_name, 'w')

    file.write("# Imports\n")
    file.write("import sys\n")
    file.write("sys.path.insert(0, r'C:\livestock3d')\n")
    file.write("import livestock3d as ls\n")

    file.write("# Run function\n")
    file.write("ls.my_function(r'" + path + "')\n")

    file.write("# Announce that template finished and create out file\n")
    file.write("print('Finished with template')\n")


    return file_name

The function takes a path as an input. The path specifies, where the template should be written. We define a variable with the file name of the template and creates that file with the open statement.

To let Python know that we want to use scripts from the C:\livestock3d folder, we need to add it to the PYTHONPATH. We do that with sys.path.insert(). After that we can import livestock3d.

After the imports we can call the function my_function from livestock3d. The function is not yet created, but we will do that in the next paragraph.

Livestock3D in CPython

We have now written both the code for the component and the template. The only piece missing is the CPython part. The CPython code is what does the actual functionality that we want. In this case to duplicate a text string. We will write the code in the C:\livestock3d\ file.

def my_function(folder):

    file = open(folder + '/data_file.txt', 'r')
    my_lines = [line.strip()
                for line in file.readlines()]

    repeat = int(my_lines[1].strip())
    line_to_write = my_lines[0].strip()

    result_file = open(folder + '/result.txt', 'w')

    for i in range(repeat):
        result_file.write(line_to_write + '\n')


    return None

my_function takes a path to a folder as input. It assumes that there is a file in that folder called: "data_file.txt". That file is created by the Grasshopper component, so make sure that the name is correct, otherwise my_function() can not run. After opening data_file.txt, the code turns the file into a list called my_lines. To be explicit we name two variables: "line_to_write" and "repeat". They are the first and second line in the list, respectively. Then we open "result.txt" and we write "line_to_write" "repeat" number of times. Thereafter, the file is closed and we are done.

Now we should test our Grasshopper component! We will do that in the next post. First Component Run