give a variable to an operator For a workflow tool I made a panel in which it displays each separate library that is linked in my file. For each library I want to add some buttons that does stuff to the library in question.

So in this example I have my panel which shows for example 2 libraries and for each one it creates a "reload" button.

Now my question is.. How do I make it so the reload button only reloads the library I want to reload? I would probably have to give the button an id or something so it knows for which library it was created...

my code so far:

import bpy

libs = bpy.data.libraries

class Reloadlib(bpy.types.Operator):
    """Reloads the current Library"""
    bl_idname = "my.reload_lib"
    bl_label = "Reload"

    def execute(self, context):
        libs[?????].reload()
        self.report({'INFO'}, 'Reloading ' + libs[?????].name)
        return {'FINISHED'}

class LibPanel(bpy.types.Panel):
    """Creates a Panel in the scene context of the properties editor"""
    bl_label = "Scene Libraries"
    bl_idname = "SCENE_PT_layout"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "scene"

    def draw(self, context):
        layout = self.layout
        scene = context.scene
        layout.label(text="Libraries:")

        for i in libs:
            layout.label(text= i.name.replace(".blend",""))
            row = layout.row()
            sub = row.row()
            sub.operator("my.reload_xref", icon = "FILE_REFRESH")

def register():
    bpy.utils.register_class(Reloadlib)
    bpy.utils.register_class(LibPanel)

def unregister():
    bpy.utils.unregister_class(Reloadlib)
    bpy.utils.unregister_class(LibPanel)

if __name__ == "__main__":
    register()


Where the question marks are is where I should be able to make the difference between the first [0] or second [1] library in the libs[] array.

In future I would also like to ad an 'open' and an 'unlink' button for each library so I can make changes to the other file. But this works by the same principle as the reload button.
I'm presuming that reload_xref is meant to be reload_lib.

In your Reloadlib class you can create a StringProperty to pass the name of the library into:

class Reloadlib(bpy.types.Operator):
    """Reloads the current Library"""
    bl_idname = "my.reload_lib"
    bl_label = "Reload"

    #2.8
    library_name : bpy.props.StringProperty()
    #2.79
    #library_name = bpy.props.StringProperty()


Then in execute you can access this local property with self.library_name:

    def execute(self, context):
        libs[self.library_name].reload()
        self.report({'INFO'}, 'Reloading ' + libs[self.library_name].name)
        return {'FINISHED'}


Then, when you display the operator you can pass in the name:

for i in libs:
    layout.label(text= i.name.replace(".blend",""))
    row = layout.row()
    sub = row.row()
    operator = sub.operator("my.reload_xref", icon = "FILE_REFRESH")
    operator.library_name = i.name


(To be clear, I haven't tested the specific functionality of reloading libraries, but  this is how you pass data generally.)

Full code: 

import bpy

libs = bpy.data.libraries

class Reloadlib(bpy.types.Operator):
    """Reloads the current Library"""
    bl_idname = "my.reload_lib"
    bl_label = "Reload"

    #2.8
    library_name : bpy.props.StringProperty()
    #2.79
    #library_name = bpy.props.StringProperty()

    def execute(self, context):
        libs[self.library_name].reload()
        self.report({'INFO'}, 'Reloading ' + libs[self.library_name].name)
        return {'FINISHED'}

class LibPanel(bpy.types.Panel):
    """Creates a Panel in the scene context of the properties editor"""
    bl_label = "Scene Libraries"
    bl_idname = "SCENE_PT_layout"
    bl_space_type = 'PROPERTIES'
    bl_region_type = 'WINDOW'
    bl_context = "scene"

    def draw(self, context):
        layout = self.layout
        scene = context.scene
        layout.label(text="Libraries:")

        for i in libs:
            layout.label(text= i.name.replace(".blend",""))
            row = layout.row()
            sub = row.row()
            operator = sub.operator("my.reload_lib", icon = "FILE_REFRESH")
            operator.library_name = i.name

def register():
    bpy.utils.register_class(Reloadlib)
    bpy.utils.register_class(LibPanel)

def unregister():
    bpy.utils.unregister_class(Reloadlib)
    bpy.utils.unregister_class(LibPanel)

if __name__ == "__main__":
    register()