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_project – Ends the running project.

• 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	THe unit that represents the wait time: MSEC - milliseconds SECONDS

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

# VR threads — Do not delete
vr_thread(main)

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).

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

# VR threads — Do not delete
vr_thread(main)

def main():
    # Print each item in the list
    colors = ["Red", "Green", "Blue"]

    for color in colors:
        brain.print(color)
        brain.new_line()

# VR threads — Do not delete
vr_thread(main)

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.

def main():
    # Turn right until facing south
    while True:
        if drivetrain.heading(DEGREES) < 180:
            drivetrain.turn_for(RIGHT, 90, DEGREES)
        wait(0.1, SECONDS)

# VR threads — Do not delete
vr_thread(main)

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.

def main():
    # Drive after turning around
    while True:
        if drivetrain.rotation(DEGREES) < 180:
            drivetrain.turn_for(RIGHT, 90, DEGREES)
        else:
            drivetrain.drive(FORWARD)
        wait(0.1, SECONDS)

# VR threads — Do not delete
vr_thread(main)

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.

def main():
    # Move depending on the detected color
    while True:
        if front_eye.detect(RED):
            drivetrain.drive(FORWARD)
        elif front_eye.detect(GREEN):
            drivetrain.drive(REVERSE)
        else:
            drivetrain.turn(RIGHT)
        wait(0.1, SECONDS)

# VR threads — Do not delete
vr_thread(main)

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.

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

# VR threads — Do not delete
vr_thread(main)

def main():
    # Wait until an object is detected to stop driving
    drivetrain.drive(FORWARD)
    while not front_distance.found_object():
        wait(50, MSEC)
    drivetrain.stop()

# VR threads — Do not delete
vr_thread(main)

break

break exits a loop immediately.

def main():
    # Stop turning after a button is pressed
    while True:
        drivetrain.turn(RIGHT)
        if front_distance.found_object():
            break
    drivetrain.stop()

# VR threads — Do not delete
vr_thread(main)

stop_project

stop_project ends a running project.

Usage:
stop_project()

Parameters	Description
	This method has no parameters.

def main():
    # Stop the project after a button is pressed
    while True:
        drivetrain.turn(RIGHT)
        if front_distance.found_object():
            stop_program()
        drivetrain.drive(FORWARD)

# VR threads — Do not delete
vr_thread(main)

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