Access to __name__ in block code?

[derrickgw]

Is there anyway to access the __name__ variable so that the block code can execute a function only if it is being executed directly?

I am using pybricks blocks for an FLL team for 4 graders. It has been working great, but now we need to combine everyone's program with a top-level menu. I foolishly assumed that we could just import all the mission files, and then use the menu to select which one to run. While this would infact be trivial if we were using code, I can't figure out how to do it with blocks.

I have several groups working on the code, and combining the code into a single file is not really a viable solution. Inevitably somebody's code is going to get messed up/deleted. It is much safer if they all work in their own file.

The Ideal situation:
When each group is coding, they have their own file that they can safely delete anything without messing up anyone else's code. They can hit "play" without the confusion of switching to some other file. Then when we move from debug to competition practice, they run the top level file, hit play, and get a menu. This would be trivial if the block task code can read the __name__ variable somehow.
Honestly, I am surprised the default behavior of the "program" block isn't a if __name__ == "__main__": block in the generated python, as that would be a more intuitive experience when importing block code.

Another potential solution that could work is if I can pin the top-level program so that hitting play always downloads the pinned program instead of the currently visible program.

Right now the only solution I have involves the kids constantly switching between the top level file and the task file they are currently editing. This is extra confusing to the younger kids because the top level file can't be blocks.

[donmerendolo]

We ran into the same problem in my team, and the solution we found was kinda hacky. Basically, use a number in the hub storage to detect if the program was being run individually or being imported in the menu. Something like this:

In the menu program:

hub.system.storage(0, write=(1).to_bytes(1, "little"))
from program_1 import program_1
# Rest of the programs
hub.system.storage(0, write=(0).to_bytes(1, "little"))

And in each individual programs for the launches (for example, program_1.py):

if int.from_bytes(hub.system.storage(0, read=1), "little") == 0:
    # If it reads 0, the program is being launched directly.
    # If it reads 1, it's being imported in the menu.
    program_1()

With function program_1 having the actual code for the robot.

IIRC, we also used a "dummy" hub object to write and read the storage, but I'm not sure if that was necessary.

[laurensvalk]

assumed that we could just import all the mission files, and then use the menu to select which one to run. While this would infact be trivial if we were using code, I can't figure out how to do it with blocks.

You can technically do that like this. The main program will be a Python listing of the file, but all the programs can use blocks as illustrated in that example.

(I can see this is confusing. In the mean time, we're working on alternatives to simplify this, no menu program required.)

Is there anyway to access the __name__ variable

I don't know exactly what you would like to build, but yes you could make an is_main block available to all your programs, like this:

[derrickgw]

That works great! The eval trick is what I was missing.

The current menu example is good, but conveniently each sub-program uses different ports. If two programs use the same port, there is an error when they are imported. I have awkwardly worked around this by defining the robot connections in a team_robot.py file that gets imported by the block code, then using those as variables. It is clumsy, but I think the kids will be able to figure it out. Something that is trivial in code: just a from team_robot import *.

Maybe next year I will work harder on trying to get them to use python. 😬

I have also used a dict to hold all the tasks for the menu. I am hoping this makes it easier for the kids to manage the menu by having a single place to define all the tasks, even though it does require a consistent function interface.

# menu.py
from pybricks.hubs import ThisHub
from pybricks.tools import hub_menu
from pybricks.parameters import Icon

hub = ThisHub()

from team_robot import *


from task1 import arm_task,drive_task


programs = {
    "1": arm_task, 
    "2": drive_task,
    "3": print
}


def exec_menu(selected):
    # Based on the selection, run a program.
    if selected == "1":
        print("run 1")
        hub.display.icon(Icon.CIRCLE)
        # print(globals())
        programs["1"](drive_base, left_arm, right_arm)
        # my_task(drive_base)            
    
    elif selected == "2":
        hub.display.icon(Icon.CIRCLE)
        print("2")
    elif selected == "L":
        import light


keys = [n for n in programs.keys()]
index = 1
def menu():
    global index

    # Make a menu to choose a letter. You can also use numbers.
    # start with the most recently seleted program
    selection = keys[index:] + keys[:index] 
    selected = hub_menu(*selection)
    index = keys.index(selected)
    
    # exec_menu(selected)
    hub.display.icon(Icon.CIRCLE)
    programs[selected](drive_base, left_arm, right_arm)


if __name__ == "__main__":
    while True:
        menu()

# team_robot.py
from pybricks.parameters import Direction, Port
from pybricks.pupdevices import Motor
from pybricks.robotics import DriveBase

left = Motor(Port.C, Direction.COUNTERCLOCKWISE)
right = Motor(Port.D, Direction.CLOCKWISE)
drive_base = DriveBase(left, right, 56, 114)
left_arm = Motor(Port.A, Direction.CLOCKWISE)
# right_arm = Motor(Port.B, Direction.CLOCKWISE)
right_arm = None


def is_main():
    return eval("__name__") == "__main__"

[laurensvalk]

That works great! The eval trick is what I was missing.

Glad it worked!

Since you seem to be an experienced coder, perhaps you'd like to try the upcoming menu solution too. I'd be interested to hear what your students think.

To try it, you can now install the very latest experimental firmware using these instructions. Once installed, you can toggle between 5 code slots using the hub buttons. When you press the ▶ icon in the app, it will go into that slot.

(You can revert to the normal firmware any time you like by reinstalling firmware the normal way. Caveats:
We changed a lot of other functions too, so don't switch to this version two days before competition day 😄 )