How to import a STL file using the file browser?

Question

I'm trying to import a stl file manually via python. My code below is pretty straight forward, but I'm struggling with the following line. I'm not sure about the syntax and format of the arguments:

bpy.ops.import_mesh.stl(filepath=???, files=???)

The current state of my operator:

import bpy
class FILE_OT_import_stl(bpy.types.Operator):
bl_idname = "file.import_model_stl"
bl_label = "Import Model STL"
bl_options = {'REGISTER', 'UNDO'} # Must have REGISTER!   

def execute(self, context):
    #my_filepath = 'K:/PQJ/Mold Generator/Blender test/'
    #filepath = '//898L-OutputModel-SLA[]_09'
    #print(filepath)
    all_files=[bpy.types.Scene.import_path]
    #print(file[0])
    bpy.ops.import_mesh.stl(filepath=my_filepath, files=all_files)
    return {'FINISHED'}


class FILE_PANEL_PT_import_export(bpy.types.Panel):
    bl_label = "Import/Export"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    # bl_context = "object" # object vs edit mode
def draw(self, context):
    layout = self.layout
    layout.label(text="Import")

    layout.prop(context.scene, "import_path")
    row = layout.row()                
    row.operator("file.import_model_stl")


classes = (
    FILE_OT_import_stl,
    FILE_PANEL_PT_import_export
)
def register():
    for cls in classes:
        bpy.types.Scene.import_path = bpy.props.StringProperty(name='Import path', subtype='FILE_PATH')
        bpy.utils.register_class(cls)
def unregister():
    del bpy.types.Scene.import_path
    for cls in classes:
        bpy.utils.unregister_class(cls)
if name == "main":
    register()

Q: How to import a certain STL file using the file browser (and add a custom material)?

Answer 1

You can just add the built-in operator import_mesh.stl to your draw method of your panel which will open up the File Browser as usual and allows the user to select one .stl file:

import bpy
class OBJECT_PT_CustomPanel(bpy.types.Panel):
    bl_label = "My Panel"
    bl_idname = "OBJECT_PT_custom_panel"
    bl_space_type = "VIEW_3D"

    bl_region_type = "UI"
    bl_category = "Tools"
    bl_context = "objectmode"
def draw(self, context):
    layout = self.layout
    #layout.operator_context = 'INVOKE_DEFAULT' #'INVOKE_AREA'
    layout.operator("import_mesh.stl", text="New", icon='FILE_NEW')


def register():
    bpy.utils.register_class(OBJECT_PT_CustomPanel)
def unregister():
    bpy.utils.unregister_class(OBJECT_PT_CustomPanel)
if name == "main":
    register()

Related: How to call a confirmation dialog box?

---

In case you want to import and modify the .stl object for whatever reason, have a look into the Operator File Import template (operator_file_import.py) that comes with Blender.

Demo operator based on the template, allows to import the file, print the object reference and assigns a new material to the incoming object in one go:

# ImportHelper is a helper class, defines filename and
# invoke() function which calls the file selector.
from bpy_extras.io_utils import ImportHelper
from bpy.types import Operator
class ImportSomeData(Operator, ImportHelper):
    """This appears in the tooltip of the operator and in the generated docs"""
    bl_idname = "import_test.some_data"
    bl_label = "Import Some Stl File"
    bl_options = {'REGISTER', 'UNDO'}
# ImportHelper mixin class uses this
filename_ext = ".stl"
filter_glob: bpy.props.StringProperty(
            default="*.stl",
            options={'HIDDEN'})

def execute(self, context):
    if self.filepath:
        bpy.ops.import_mesh.stl(filepath=self.filepath)
        # Print the imported object reference
        print ("Imported object:", context.object)
        # Create a material
        mat = bpy.data.materials.new(name="STLMaterial")
        # Append the material to the last slot
        context.object.data.materials.append(mat)

    return {'FINISHED'}

Further reading:

• How to assign a new material to an object in the scene from Python?
• Import multiple STL files and modify the incoming objects in one go?