How to put buttons, sliders, ect. in the N panel with an addon [duplicate]

Question

My goal is to make an addon that makes a new tab in the sidebar with sliders and buttons and stuff that do nothing (it’s my first addon, so I’m just experimenting).

I stole some code from the cursor array addon tutorial found on the Blender documentation just to get the first button made (which I could only figure out how to put in the VIEW3D_PT_view3d_properties part of the side panel). Here is my code thus far.

I’m pretty sure I could figure out how to make all the buttons if I could figure out how to register and unregister multiple classes (as you can see, class pan is unregistered).

_{I am a beginner with Python so try to answer in simplest terms.}

Answer 1

Here is a very trivial very small very complete add-on. It draws one button in one panel that shows up as the "TLA" tab in the 3D Viewport when the Viewport is in Object Mode. It only has two classes, but it uses a common technique to register multiple classes by putting their names in an array and processing the array.

For each button you want, add an operator Class with a different name and a new col.operator.

# Very small add on to start from

bl_info = {
    "name" : "draw colors",
    "description" : "A skeleton addon",
    "author" : "Marty",
    "version" : (0, 0, 1),
    "blender" : (2, 80, 0),
    "location" : "View3D",
    "warning" : "",
    "support" : "COMMUNITY",
    "doc_url" : "",
    "category" : "3D View"
}

import bpy
from bpy.types import Operator
from bpy.types import Panel

class TLA_OT_operator(Operator):
    """ tooltip goes here """
    bl_idname = "demo.operator"
    bl_label = "I'm a Skeleton Operator"
    bl_options = {"REGISTER", "UNDO"}

    @classmethod
    def poll(cls, context):
        return context.mode == "OBJECT"

    def execute(self, context):

        self.report({'INFO'},
            f"execute()")

        return {'FINISHED'}


class TLA_PT_sidebar(Panel):
    """Display test button"""
    bl_label = "TLA"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"
    bl_category = "TLA"

    def draw(self, context):
        col = self.layout.column(align=True)
        prop = col.operator(TLA_OT_operator.bl_idname, text="Say Something")

 
classes = [
    TLA_OT_operator,
    TLA_PT_sidebar,
]

def register():
    for c in classes:
        bpy.utils.register_class(c)


def unregister():
    for c in classes:
        bpy.utils.unregister_class(c)


if __name__ == '__main__':
    register()

Answer 2

Here I have extended Marty's answer with bool and float properties:

import bpy

bl_info = {
    "name" : "whatever",
    "description" : "addon",
    "author" : "Marty",
    "version" : (0, 0, 1),
    "blender" : (2, 80, 0),
    "location" : "View3D",
    "warning" : "",
    "support" : "COMMUNITY",
    "doc_url" : "",
    "category" : "3D View"
}

import bpy
from bpy.types import Operator
from bpy.types import Panel

class TLA_OT_operator(Operator):
    """ tooltip goes here """
    bl_idname = "demo.operator"
    bl_label = "I'm a Skeleton Operator"
    bl_options = {"REGISTER", "UNDO"}

    @classmethod
    def poll(cls, context):
        return context.mode == "OBJECT"

    def execute(self, context):

        self.report({'INFO'},
            f"execute()")

        return {'FINISHED'}


class TLA_PT_sidebar(Panel):
    """Display test button"""
    bl_label = "TLA"
    bl_space_type = "VIEW_3D"
    bl_region_type = "UI"
    bl_category = "TLA"

    def draw(self, context):
        col = self.layout.column(align=True)
        prop = col.operator(TLA_OT_operator.bl_idname, text="Say Something")
        
        col.prop(context.scene, "my_tool")
        col.prop(context.scene, "my_float")

 
classes = [
    TLA_OT_operator,
    TLA_PT_sidebar,
]

def register():
    
    for c in classes:
        bpy.utils.register_class(c)
    bpy.types.Scene.my_tool = bpy.props.BoolProperty(
        name='Bool',
        default=False
    )
    bpy.types.Scene.my_float = bpy.props.FloatProperty(
        name='Float',
        default=0.0 
    )
        
def unregister():
    del bpy.types.Scene.my_float
    del bpy.types.Scene.my_bool
    for c in classes:
        bpy.utils.unregister_class(c)


if __name__ == '__main__':
    register()

result: