How can I extend the unit selection logic in my RTS game to apply to multiple units?

Update:
I've now made classes and objects to hold the unit positions, and I can blit several to the screen and move them all at once. However what I haven't been able to do is get the units to be selected independently. I have these lists/arrays which draw from classes:

unit_orc_grunt = Unit("Grunt",[35,70,105,140,175,210,245,280,315,350],[35,70,105,140,175,210,245,280,315,350])



positions = numpy.array([

                            [unit_orc_grunt.locationx[0],unit_orc_grunt.locationy[0]],

                            [unit_orc_grunt.locationx[1],unit_orc_grunt.locationy[1]],

                            [unit_orc_grunt.locationx[2],unit_orc_grunt.locationy[2]],

                            [unit_orc_grunt.locationx[3],unit_orc_grunt.locationy[3]],

                            [unit_orc_grunt.locationx[4],unit_orc_grunt.locationy[4]],

                            [unit_orc_grunt.locationx[5],unit_orc_grunt.locationy[5]],

                            [unit_orc_grunt.locationx[6],unit_orc_grunt.locationy[6]],

                            [unit_orc_grunt.locationx[7],unit_orc_grunt.locationy[7]],

                            [unit_orc_grunt.locationx[8],unit_orc_grunt.locationy[8]],

                            [unit_orc_grunt.locationx[9],unit_orc_grunt.locationy[9]],

                        ])



not_selected = [

                    positions[0],

                    positions[1],

                    positions[2],

                    positions[3],

                    positions[4],

                    positions[5],

                    positions[6],

                    positions[7],

                    positions[8],

                    positions[9]

                ]



selected = []

Then I have this in the loop:

        elif button_type[0] == 1:

            for position in positions:

                    if numpy.any(position) == numpy.any(not_selected) and numpy.any(position) != numpy.any(selected) and mouse_position[0] >= position[0] and mouse_position[0] <= position[0] + character_width and mouse_position[1] >= position[1] and mouse_position[1] <= position[1] + character_height:

                        selected.append(position)

                        not_selected.remove(position)

The selected units would then be drawn from the list 'selected', however, I am getting an error:

The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

------------------Original question----------------------

Currently if you left-click on the unit, it becomes 'selected' (or 'de-selected'), and a green square is drawn around it. Then when you right-click somewhere on the screen, the unit moves neatly into the square in the location that you clicked.

Also if you use the up, down, left or right keys it will scroll the screen.

import pygame

import random

pygame.init()



#Define mouse position

mouse_position_x = 525

mouse_position_y = 315



# Define colors

green = (0,255,0)

brown = (150,75,0)



#Define border position

border_x = 0

border_y = 0



#Define character selection box

def character_selection_box():

    pygame.draw.line(screen,green,(character_location_x,character_location_y),(character_location_x+character_width,character_location_y),2) # Top bar

    pygame.draw.line(screen,green,(character_location_x,character_location_y+character_height),(character_location_x+character_width,character_location_y+character_height),2) # Bottom bar

    pygame.draw.line(screen,green,(character_location_x,character_location_y),(character_location_x,character_location_y+character_height),2) # Left bar

    pygame.draw.line(screen,green,(character_location_x+character_width,character_location_y),(character_location_x+character_width,character_location_y+character_height+1),2) # Right bar



#Define round

def assign_square(n):

    div = (n/35)

    rou = round(div)

    mul = (35*rou)

    return int(mul)



#Set window

screen_width = 981

screen_height = 700

game_screen_width = 800

game_screen_height = 700

screen_size = (screen_width,screen_height)

screen = pygame.display.set_mode(screen_size)

pygame.display.set_caption("Warpath")



#Set block character

character_width = 35

character_height = 35

character_location_x = 525

character_location_y = 315

movement = 1

unit_selected = 0



#Load images

orc_grunt_forward = pygame.image.load('orc_forward3.png') #(35 by 35 pixel image)

character_image = orc_grunt_forward



#Loop until the user clicks the close button

shutdown = False



#Set clock

clock = pygame.time.Clock()



#Set scroll limit

scroll_x = 0

scroll_y = 0



 # ---------- Main program loop -----------

while not shutdown:



    # --- Main event loop ---

    for event in pygame.event.get():



        # --- If quit button pressed, shutdown

        if event.type == pygame.QUIT: 

            shutdown = True



        # --- If mouse button pressed

        elif event.type == pygame.MOUSEBUTTONDOWN: # If a mouse button is pressed

            mouse_position = pygame.mouse.get_pos() # Get mouse position

            button_type = pygame.mouse.get_pressed() # Check which button was pressed



            # --- If left click pressed and the curser was on a character, select that character 

            if button_type[0] == 1 and mouse_position[0] >= character_location_x and mouse_position[0] <= character_location_x + character_width and mouse_position[1] >= character_location_y and mouse_position[1] <= character_location_y + character_height:

                print("Unit selected",unit_selected)

                print(button_type)

                unit_selected += 1

                unit_selected /= unit_selected #(Otherwise it will add up unit selected if you click more than once)

                int(unit_selected)



            # --- If right click pressed and a character was selected (and it's within the game screen), move the character to the location     

            elif button_type[2] == 1 and unit_selected == 1 and mouse_position[0] > 175: 

                mouse_position_x *= 0

                mouse_position_y *= 0



                if mouse_position[0] >= assign_square(mouse_position[0]):

                    mouse_position_x += assign_square(mouse_position[0])



                elif mouse_position[0] <= assign_square(mouse_position[0]):

                    mouse_position_x -= 35

                    mouse_position_x += assign_square(mouse_position[0])



                if mouse_position[1] >= assign_square(mouse_position[1]):

                    mouse_position_y += assign_square(mouse_position[1])



                elif mouse_position[1] <= assign_square(mouse_position[1]):

                    mouse_position_y -= 35

                    mouse_position_y += assign_square(mouse_position[1])



            # --- If left click pressed and the curser was not on a character, deselect the character        

            elif button_type[0] == 1 and mouse_position[0] < character_location_x or mouse_position[0] > character_location_x + character_width or mouse_position[1] < character_location_y or mouse_position[1] > character_location_y + character_height:

                print("Unit not selected")

                print(button_type)

                unit_selected *= 0

                int(unit_selected)



        # --- If key pressed, scroll the screen

        elif event.type == pygame.KEYDOWN:



            if event.key == pygame.K_RIGHT and scroll_x > -10:

                direction = "right"

                character_location_x -= 35

                mouse_position_x -= 35

                border_x -= 35

                scroll_x -= 1



            if event.key == pygame.K_LEFT and scroll_x < 10:

                direction = "left"

                character_location_x += 35

                mouse_position_x += 35

                border_x += 35

                scroll_x += 1



            if event.key == pygame.K_UP and scroll_y < 10:

                direction = "up"

                character_location_y += 35

                mouse_position_y += 35

                border_y += 35

                scroll_y += 1



            if event.key == pygame.K_DOWN and scroll_y > -10:

                direction = "down"

                character_location_y -= 35

                mouse_position_y -= 35

                border_y -= 35

                scroll_y -= 1



    # --- Game logic ---



    # --- Set character movement      

    if character_location_x < mouse_position_x:

        character_location_x += movement

    if character_location_x > mouse_position_x:

        character_location_x -= movement

    if character_location_y < mouse_position_y:

        character_location_y += movement

    if character_location_y > mouse_position_y:

        character_location_y -= movement



    # --- Drawing ---

    screen.fill(brown) # Draw background

    screen.blit(character_image,(character_location_x,character_location_y)) # Draw character



    if unit_selected == 1: 

        character_selection_box() # Draw character selection box if unit is selected



    clock.tick(30)

    pygame.display.flip()



#Shutdown

if shutdown == True:

    pygame.quit()

The problem is that I can't figure out how to extend this to multiple units - currently if I want to add more units I can only either manage to:

a) Move them all at once

or

b) Paste the same code multiple times adjusting the character variable (not a robust / scalable solution)

How can I adjust my code so that I have a scalable solution where:

1) I can select a single unit and move it, without moving every unit at once

2) I can select multiple units by clicking on each one individually, and move them all at once (not worrying about pathfinding right now)

I also tried using classes to achieve this but it still felt like I was copying / pasting multiple functions rather than having a robust solution.

I've removed any code that doesn't concern the issue while keeping a functioning program.

Thanks