The code for an add-on that generates 100 spheres at random locations in a 20 x 20 space at the center of a Blender scene.

Firefly.py

bl_info = {
    "name": "Fireflies",
    "author": "GifGuide2Code",
    "version": (1,0,0),
    "category": "Object",
    }

import bpy
import random

class fireflies(bpy.types.Operator):
    """Fireflies"""
    bl_idname = "object.fireflies"
    bl_label = "Create fireflies"
    
    def execute(self, context):
        x=1
        y=1
        z=1
        for index in range(100):
            bpy.ops.mesh.primitive_uv_sphere_add(size=.02,location=(x,y,z))
            x=random.randint(-10,10)
            y=random.randint(-10,10)
            z=random.randint(-10,10)
        return{'FINISHED'}

def register():
    bpy.utils.register_class(fireflies)

def unregister():
    bpy.utils.register_class(fireflies)
    
if __name__ == "__main__":
    register()