Control

Introduction

Control in Python lets you tell the robot when to wait, when to repeat actions, how to make decisions, and when to end the project.

Below is a list of available controls, including methods and core Python keywords:

• wait — Pauses the project for a given time.

• for — Repeats code for each item in a sequence.

• if — Runs code if a condition is true.

• if/else — Runs different code depending on a condition.

• if/elif/else — Checks multiple conditions in order.

• while — Repeats code while a condition is true.

• break — Exits a loop immediately.

• stop_program — Ends the running program.

• pass — Placeholder used when no action is needed.

wait

wait pauses for a specific amount of time before moving to the next line of code.

Usage:
wait(time, units)

Parameters	Description
time	The amount of time to wait, as a positive whole number or decimal.
units	The unit that represents the wait time: MSEC (default) – milliseconds, or SECONDS

# Turn right for one second, then stop
drivetrain.turn(RIGHT)
wait(1, SECONDS)
drivetrain.stop()

for

for repeats a set of actions a specific number of times. for can be used to loop through items in lists, tuples, dictionaries, sets, strings, or for a specified amount of loops with range.

Usage:

for value in expression_list:
    pass

Components	Description
value	A temporary variable that stores the current element in the iteration.
expression_list	The collection of elements being looped through (e.g., list, string, range).

# Move in a square path
for index in range(4):
    drivetrain.drive_for(FORWARD, 100, MM)
    drivetrain.turn_for(RIGHT, 90)

# Print each item in the list
colors = ["Red", "Green", "Blue"]

for color in colors:
    brain.screen.print(color)
    brain.screen.next_row()

if

if runs the indented block of code if the condition is True.

Usage:

if condition:
    pass

Components	Description
condition	An expression or variable that is checked when the statement runs. If it is True, the code inside the if block executes; if it is False, the block is skipped.

# Turn right when a button is pressed
while True:
    if brain.buttonCheck.pressing():
        drivetrain.turn_for(RIGHT, 90)
    wait(0.1, SECONDS)

if/else

if and else determine which indented block of code runs based on whether the condition is True or False.

Usage:

if condition:
    pass
else:
    pass

Components	Description
condition	An expression or variable that is checked when the statement runs. If it is True, the code inside the if block executes; if it is False, the code inside the else block executes instead.

# Turn right when a button is pressed, and remain still
# when the button is not pressed
while True:
    if brain.buttonCheck.pressing():
        drivetrain.turn(RIGHT)
    else:
        drivetrain.stop()
    wait(0.1, SECONDS)

if/elif/else

The if/elif/else structure selects which indented block of code runs based on conditions:

• if runs its block if the condition is True.

• elif checks additional conditions only if all previous conditions are False. Multiple elif statements can be used.

• else runs its block only if none of the previous conditions are True.

Usage:

if condition:
    pass
elif condition:
    pass
else:
    pass

Components	Description
condition	An expression or variable that is checked when the statement runs. The first condition that is True determines which block executes; if none are True, the else block runs.

# Turn depending on what button is pressed
while True:
    if brain.buttonRight.pressing():
        drivetrain.turn(RIGHT)
    elif brain.buttonLeft.pressing():
        drivetrain.turn(LEFT)
    else:
        drivetrain.stop()
    wait(0.1, SECONDS)

while

while repeatedly runs code as long as the condition is True. It can also be used like a “forever” by using True as the condition, or a “wait until” by adding not to the condition, as shown in the examples below.

Usage:

while condition:
    pass

Components	Description
condition	An expression or variable that is checked before each iteration. If it is True, the loop continues; if it is False, the loop stops.

# Keep the screen green while the robot is moving
drivetrain.drive_for(FORWARD, 200, MM, wait=False)
while drivetrain.is_moving():
    brain.screen.clear_screen(Color.GREEN)
    wait(50, MSEC)

brain.screen.clear_screen(Color.BLACK)

while True:
    # Move in a square path forever
    drivetrain.drive_for(FORWARD, 150, MM)
    drivetrain.turn_for(RIGHT, 90)

# Wait until a button is pressed to stop driving
drivetrain.drive(FORWARD)
while not brain.buttonCheck.pressing():
    wait(50, MSEC)
drivetrain.stop()

break

break exits a loop immediately. break can be used to leave loops that otherwise would loop forever.

# Stop turning after a button is pressed
while True:
    drivetrain.turn(RIGHT)
    if brain.buttonCheck.pressing():
        break
drivetrain.stop()
brain.play_sound(SoundType.POWER_DOWN)

stop_program

program_stop ends a running project.

Usage:
brain.program_stop()

Parameters	Description
	This method has no parameters.

# Stop the project after a button is pressed
while True:
    drivetrain.turn(RIGHT)
    if brain.buttonCheck.pressing():
        brain.program_stop()
    brain.play_sound(SoundType.POWER_DOWN)

pass

pass is a placeholder for future code and can be used to avoid errors in empty loops, conditionals, and functions.

if condition:
    pass

def function():
    pass