Why can't I run this Python Script to export the drawn parts to an .stl file?

Question

I'm new to blender as I am trying to create a simple Robot skeleton using the Blender Python API (bpy). However, when I run the python script the console spits out the following error:

Traceback (most recent call last): File "", line 1, in NameError: name 'Robot' is not defined

How can I fix this error? I don't understand what it means when it says that the name 'Robot' is now defined. I am also using Blender 2.7.7 on Ubuntu 18.04

The following is my code:

import bpy

#this function will draw a cylinder and cut portions from opposite sides to create the base plate
def Draw_Base_Plate():

        #create two cubes and then we'll "Subtract" them from the base plate
        #then we will delete the cubes
        bpy.ops.mesh.primitive_cube_add(radius = 0.05, location = (0.175, 0, 0.09))
        bpy.ops.mesh.primitive_cube_add(radius = 0.05, location = (-0.175, 0, 0.09))

        ############################################################################

        #adding the base plate itself
        bpy.ops.mesh.primitive_cylinder_add(radius = 0.15, depth = 0.05, location = (0,0,0.09))

        #adding boolean difference modifier from the first cube
        bps.ops.object.modifier_add(type = 'BOOLEAN')
        bpy.context.object.modifiers["Boolean"].operation = 'DIFFERENCE'
        bpy.context.object.modifiers["Boolean"].object = bpy.data.objects["Cube"]
        bpy.ops.object.modifier_apply(modifier = "Boolean")

        ###########################################################################

        #adding boolean difference modifier from the second cube
        bps.ops.object.modifier_add(type = 'BOOLEAN')
        bpy.context.object.modifiers["Boolean"].operation = 'DIFFERENCE'
        bpy.context.object.modifiers["Boolean"].object = bpy.data.objects["Cube.001"]
        bpy.ops.object.modifier_apply(modifier = "Boolean")

        ###########################################################################

        #deselect cylinder and delete cubes
        bpy.ops.object.select_pattern(pattern = "Cube")
        bpy.ops.object.select_pattern(pattern = "Cube.001")
        bpy.data.objects['Cylinder'].select = False
        bpy.ops.object.delete(use_global = False)

        ###########################################################################       

#this function will motors and wheels attached to the base plate    
def Draw_Motor_Wheels():

    #draw a cylinder with 0.045 of radius and 0.01 meters in depth for the wheels
    #once we create the wheels it will be rotated and translated into the
    #cut portion of the base plate

    #create first wheel
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.045, depth = 0.01, location = (0,0,0.07))
    #rotate the first wheel
    bpy.context.object.rotation_euler[1] = 1.5708 #is this pi/2
    #translate
    bpy.context.object.location[0] = 0.135

    #create second wheel
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.045, depth = 0.01, location = (0,0,0.07))
    #rotate the first wheel
    bpy.context.object.rotation_euler[1] = 1.5708 #is this pi/2
    #translate
    bpy.context.object.location[0] = -0.135   

    #now we can create the two dummy motors and add them onto the base plate

    #adding motors
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.018, depth = 0.06, location = (0.075,0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708 #pi/2 rotation?

    bpy.ops.mesh.primitive_cylinder_add(radius = 0.018, depth = 0.06, location = (-0.075,0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708 #pi/2 rotation?

    #now we will add the shafts to the motors
    #shaft 1
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.006, depth = 0.04, location = (0.12, 0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708

    #shaft 2
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.006, depth = 0.04, location = (-0.12, 0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708

    #now we can add the 2 caster wheels    
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.015, depth = 0.05, location = (0,0.125,0.065))
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.015, depth = 0.05, location = (0,-0.125, 0.065))

    #now we'll add a dummy kinect sensor
    bpy.ops.mesh.primitive_cube_add(radius = 0.04, location = (0,0, 0.26))

#this function will draw the middle plate of the robot

def Draw_Middle_Plate():
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.15, depth = 0.005, location = (0, 0, 0.22))

#this function will draw the top plate of the robot
def Draw_Top_Plate():
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.15, depth = 0.005, location = (0, 0, 0.37))

#this function will draw support tubes connecting the plates of the robot
def Draw_Support_Tubes():
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.007, depth = 0.3, location = (0.09, 0.09, 0.23))
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.007, depth = 0.3, location = (-0.09, 0.09, 0.23))
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.007, depth = 0.3, location = (-0.09, -0.09, 0.23))
    bpy.ops.mesh.primitive_cylinder_add(radius = 0.007, depth = 0.3, location = (0.09, -0.09, 0.23))

#This function will export the newly designed robot to .STL, but we have to change the STL filepath
#executing the script

def Save_to_STL():
    bpy.ops.object.select_all(action = 'SELECT')
    #bpy.ops.object.select_all(action = 'TOGGLE')
    bpy.ops.export_mesh.stl(check_existing = True, filepath = "/home/robertek/Desktop/exported.stl", filter_glob = "*.stl", ascii = False, use_mesh_modifiers = True, axis_forward = 'Y', axis_up = 'Z', global_scale = 1.0)

#Main body code
if __name__ == "__main__":
    Draw_Base_Plate()
    Draw_Motors_Wheels()
    Draw_Middle_Plate()
    Draw_Top_Plate()
    Save_to_STL()

Answer 1

I solved the problem. I had some typos in the main body of my code and also the boolean modifiers were not correct in the code. I found another post with a similar problem, or at least, the code was utilized from the same book. Here is the stack exchange link for more info: Python script to generate robot model produces wrong result

import bpy # contains all the functionalities of Blender and it can only be
       # accessed from inside the Blender application



# This function will draw base plate
def Draw_Base_Plate(scene=bpy.context.scene):
    #Add cube for cutting sides of base plate

    bpy.ops.mesh.primitive_cube_add(radius=0.05, location=(0.175,0,0.09))
    cube1 = scene.objects.active
    # copy cube1 and link to scene (not required as example howto)

    cube2 = cube1.copy()
    cube2.location.x = -0.175
    scene.objects.link(cube2)


    #Adding base plate
    bpy.ops.mesh.primitive_cylinder_add(radius=0.15,depth=0.005, location=(0,0,0.09))
    cyl = scene.objects.active

    #Adding boolean difference modifiers
    for ob in [cube1, cube1]:
        mod = cyl.modifiers.new("FacePlateBool", type='BOOLEAN')
        mod.operation = 'DIFFERENCE'
        mod.object =  ob        
        bpy.ops.object.modifier_apply(modifier=mod.name)
        ob.location.x = -ob.location.x

    #Deselect cylinder and delete cube        
    cyl.select = False
    scene.objects.unlink(cube1)
    bpy.data.objects.remove(cube1)   

        #Adding booleab difference modifiers
    for ob in [cube2, cube2]:
        mod = cyl.modifiers.new("FacePlateBool", type='BOOLEAN')
        mod.operation = 'DIFFERENCE'
        mod.object =  ob        
        bpy.ops.object.modifier_apply(modifier=mod.name)
        ob.location.x = -ob.location.x

    #Deselect cylinder and delete cube        
    cyl.select = False
    scene.objects.unlink(cube2)
    bpy.data.objects.remove(cube2)   

#This function will draw motors and wheels
def Draw_Motors_Wheels():

    #Create first Wheel

    bpy.ops.mesh.primitive_cylinder_add(radius=0.045,depth=0.01, location=(0,0,0.07))
    #Rotate
    bpy.context.object.rotation_euler[1] = 1.5708
    #Transalation
    bpy.context.object.location[0] = 0.135

    #Create second wheel
    bpy.ops.mesh.primitive_cylinder_add(radius=0.045,depth=0.01, location=(0,0,0.07))
    #Rotate
    bpy.context.object.rotation_euler[1] = 1.5708
    #Transalation
    bpy.context.object.location[0] = -0.135

    #Adding motors

    bpy.ops.mesh.primitive_cylinder_add(radius=0.018,depth=0.06, location=(0.075,0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708

    bpy.ops.mesh.primitive_cylinder_add(radius=0.018,depth=0.06, location=(-0.075,0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708


    #Adding motor shaft
    bpy.ops.mesh.primitive_cylinder_add(radius=0.006,depth=0.04, location=(0.12,0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708

    bpy.ops.mesh.primitive_cylinder_add(radius=0.006,depth=0.04, location=(-0.12,0,0.075))
    bpy.context.object.rotation_euler[1] = 1.5708


#############################################################################################

    #Addubg Caster Wheel

    bpy.ops.mesh.primitive_cylinder_add(radius=0.015,depth=0.05, location=(0,0.125,0.065))
    bpy.ops.mesh.primitive_cylinder_add(radius=0.015,depth=0.05, location=(0,-0.125,0.065))

    #Adding Kinect

    bpy.ops.mesh.primitive_cube_add(radius=0.04, location=(0,0,0.26))    

#Draw middle plate
def Draw_Middle_Plate():
    bpy.ops.mesh.primitive_cylinder_add(radius=0.15,depth=0.005, location=(0,0,0.22))

#Adding top plate
def Draw_Top_Plate():
    bpy.ops.mesh.primitive_cylinder_add(radius=0.15,depth=0.005, location=(0,0,0.37))

#Adding support tubes
def Draw_Support_Tubes():
    #Cylinders
    bpy.ops.mesh.primitive_cylinder_add(radius=0.007,depth=0.30, location=(0.09,0.09,0.23))
    bpy.ops.mesh.primitive_cylinder_add(radius=0.007,depth=0.30, location=(-0.09,0.09,0.23))
    bpy.ops.mesh.primitive_cylinder_add(radius=0.007,depth=0.30, location=(-0.09,-0.09,0.23))
    bpy.ops.mesh.primitive_cylinder_add(radius=0.007,depth=0.30, location=(0.09,-0.09,0.23))

#Exporting into STL    
def Save_to_STL():
    bpy.ops.object.select_all(action='SELECT')
    #    bpy.ops.mesh.select_all(action='TOGGLE')
    bpy.ops.export_mesh.stl(check_existing=True, 
        filepath="/home/robertek/Desktop/exported.stl", 
        filter_glob="*.stl", ascii=False, use_mesh_modifiers=True,   
        axis_forward='Y', axis_up='Z', global_scale=1.0)


#Main code

if __name__ == "__main__":
    Draw_Base_Plate()
    Draw_Motors_Wheels()
    Draw_Middle_Plate()
    Draw_Top_Plate()
    Draw_Support_Tubes()
    Save_to_STL()