Control#

Introduction #

Control includes methods for timing, program flow, conditional logic, and project termination. These controls let you pause execution, create loops, define logic paths, and end a program. Below is a list of available controls, including methods and core Python keywords:

wait – Pauses execution for a given number of milliseconds or seconds.
for – Repeats code for each item in a sequence.
if – Executes 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 method.

Usage:
wait(time, units)

Parameters	Description
`time`	The amount of time to wait, as a positive integer.
`units`	Milliseconds `MSEC` (default) or `SECONDS`.

# Move right for one second, then stop
robot.move_at(90)
wait(1, SECONDS)
robot.stop_all_movement()

For #

for iterates over a sequence (such as a list, tuple, dictionary, set, or string) or any iterable object. It executes the block of code once for each item in the sequence.

Usage:

for value in expression_list:
    pass

Parameters	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):
    robot.move_for(50, 0)
    robot.turn_for(RIGHT, 90)

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

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

Displays three objects being printed on the screen.

If #

if executes the indented block of code if the condition evaluates as True.

Usage:

if condition:
    pass

Parameters	Description
`condition`	An expression or variable that is evaluated when the statement runs. If it evaluates as `True`, the code inside the `if` block executes; if it evaluates as `False`, the block is skipped.

# Kick when the screen is pressed
while True:
    if robot.screen.pressing():
        robot.kicker.kick(MEDIUM)
    wait(0.1, SECONDS)

If/Else #

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

Usage:

if condition:
    pass
else:
    pass

Parameters	Description
`condition`	An expression or variable that is evaluated when the statement runs. If it evaluates as `True`, the code inside the `if` block executes; if it evaluates as `False`, the code inside the `else` block executes instead.

# Show one emoji when the screen is pressed,
# and a different emoji when not pressed
while True:
    if robot.screen.pressing():
        robot.screen.show_emoji(EXCITED)

    else:
        robot.screen.show_emoji(BORED)
    
    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 evaluates as True.
elif checks additional conditions only if all previous conditions evaluated as False. Multiple elif statements can be used.
else runs its block only if none of the previous conditions evaluated as True.

Usage:

if condition:
    pass
elif condition:
    pass
else:
    pass

Parameters	Description
`condition`	An expression or variable that is evaluated when the statement runs. The first condition that evaluates as `True` determines which block executes; if none are `True`, the `else` block runs.

# Move the robot forward or reverse
# based on the position of the joystick
def when_axis_changed():
    position = controller.axis1.position()
    if position > 0:
        robot.move_at(0)
    elif position < 0:
        robot.move_at(180)
    else:
        robot.stop_all_movement()

controller.axis1.changed(when_axis_changed)

While #

while repeatedly runs methods as long as the condition is True. It can also be used like a “Wait until” by adding not to the condition, as shown in the example below.

Usage:

while condition:
    pass

Parameters	Description
`condition`	An expression or variable that is evaluated before each iteration. If it evaluates as `True`, the loop continues; if it evaluates as `False`, the loop stops.

# Keep the LEDs green while the robot is moving
robot.move_for(200, 0, wait=False)
while robot.is_move_active():
    robot.led.on(ALL_LEDS, GREEN)
    wait(50, MSEC)

robot.led.on(ALL_LEDS, BLACK)

while True:
    # Continually flash all LEDs red then green.
    robot.led.on(ALL_LEDS, RED)
    wait(0.5, SECONDS)
    robot.led.on(ALL_LEDS, GREEN)
    wait(0.5, SECONDS)

# Wait until the screen is pressed before
# turning off the LEDs
while not robot.screen.pressing():
    robot.led.on(ALL_LEDS, RED)
    wait(50, MSEC)

robot.led.on(ALL_LEDS, BLACK)

Break #

break exits a loop immediately.

# Flash LEDs until the screen is pressed
while True:
    robot.led.on(ALL_LEDS, RED)
    wait(0.5, SECONDS)
    robot.led.on(ALL_LEDS, GREEN)
    wait(0.5, SECONDS)

    if robot.screen.pressing():
        break

# Turn the LEDs Off
robot.led.off(ALL_LEDS)

Stop Program #

stop_program ends a running project.

Usage:
robot.stop_program()

Parameters	Description
	This method has no parameters.

# Stop the project once the screen is pressed
while True:
    robot.led.on(ALL_LEDS, RED)
    wait(0.5, SECONDS)
    robot.led.on(ALL_LEDS, GREEN)
    wait(0.5, SECONDS)
    if robot.screen.pressing():
        robot.stop_program()

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