Python Basics Q&A: Self-Assessment Guide

Purpose: Test your understanding of Python basics for VEX V5 robotics Total Questions: 45 (15 per topic) Estimated Time: 30-45 minutes Prerequisites: Complete Tutorials 3.1, 3.2, and 3.3

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How to Use This Guide

1. Try First: Answer each question before looking at the answer
2. Write It Down: Writing helps you remember better
3. Check Yourself: Compare to the Answer Key at the end
4. Review: Go back to the tutorial for any topics you struggled with
5. Practice: Try the code examples in VEXcode or Python

Scoring Guide

Score	What It Means
40-45 correct	Excellent! Ready for advanced topics
30-39 correct	Good understanding, review missed topics
20-29 correct	Needs more practice, re-read tutorials
Below 20	Start over with Tutorial 3.1

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Section 1: Variables and Types

Conceptual Questions (Q1-Q5)

Q1: What is a variable in Python? Explain using a real-world analogy.

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Q2: In Python, what's the difference between = (single equals) and == (double equals)?

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Q3: Why do we use ALL_CAPS names for some variables like WHEEL_TRAVEL_MM in robot_config.py?

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Q4: Name the four basic data types in Python and give one example of each that you might use in a Push Back robot.

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Q5: What happens when you run speed = speed + 10 if speed was originally 50? Walk through step by step.

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Code Reading Questions (Q6-Q10)

Q6: What is the final value of x after these lines run?

x = 10
x = x * 2
x = x - 5

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Q7: What data type is each of these variables?

a = 42
b = 3.14
c = "VEX"
d = True
e = "100"

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Q8: What does this code output?

blocks = 5
points_per_block = 3
total = blocks * points_per_block
print("Score: " + str(total))

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Q9: This code has an error. What is it, and how would you fix it?

motor_port = "1"
actual_port = motor_port + 1

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Q10: What is wrong with this variable name? How would you fix it?

my-robot-speed = 50

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Push Back Application Questions (Q11-Q15)

Q11: Write Python code to calculate your alliance's block score if you scored 8 blocks at 3 points each. Print the result.

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Q12: Create variables to store the following information about your Push Back robot: - Your team number (a whole number) - Your robot's name (text) - Whether your robot is parked in the zone (yes/no) - Your wheel diameter in inches (a decimal number)

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Q13: The Push Back field is 12 feet by 12 feet. Write Python code to: 1. Store the field size in feet 2. Convert it to millimeters (1 foot = 304.8 mm) 3. Print both values

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Q14: In Push Back, parking bonuses are: - 1 robot parked = 8 points - 2 robots parked = 30 points

Write code that stores how many robots are parked (use 2) and calculates the bonus points.

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Q15: Look at this code from robot_config.py:

WHEEL_TRAVEL_MM = 319.19
TRACK_WIDTH_MM = 295

What do these numbers represent? Why are they in ALL_CAPS? What data types are they?

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Section 2: Functions

Conceptual Questions (Q16-Q20)

Q16: What is a function in Python? Explain using the recipe analogy.

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Q17: What is the difference between a parameter and an argument? Give an example.

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Q18: Why is return important in a function? What happens if you forget it?

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Q19: What is a default parameter? Look at the deadband() function in utils.py:

def deadband(value, threshold=5.0):

What is the default value for threshold?

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Q20: In driver_control.py, motor control code is inside a function called driver_control_loop(). Why is it better to put code in a function instead of writing it directly?

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Code Reading Questions (Q21-Q25)

Q21: What does this function return when called with calculate_area(4, 5)?

def calculate_area(width, height):
    area = width * height
    return area

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Q22: This function has TWO errors. Find them both:

def add_numbers(a, b)
    result = a + b
    return result

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Q23: What does this code output? (There are two function calls)

def greet(name="Robot"):
    print("Hello, " + name + "!")

greet()
greet("Team 12345")

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Q24: Trace through deadband(3, threshold=5) step by step. What value is returned and why?

def deadband(value, threshold=5.0):
    if abs(value) < threshold:
        return 0.0
    return value

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Q25: What does clamp(150, 0, 100) return? Explain why.

def clamp(value, min_val, max_val):
    return max(min_val, min(value, max_val))

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Push Back Application Questions (Q26-Q30)

Q26: Write a function called calculate_block_score that: - Takes the number of blocks as a parameter - Returns the total points (each block is worth 3 points) - Include a docstring explaining what it does

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Q27: Write a function called check_zone_control that: - Takes two parameters: our_blocks and opponent_blocks - Returns True if we have more blocks than the opponent - Returns False otherwise

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Q28: The deadband() function helps with Push Back driving. Answer these questions: 1. What problem does it solve? 2. Why is this important when positioning blocks near goals? 3. What happens if joystick drift causes the robot to move when you're not touching it?

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Q29: Write a function called parking_bonus that: - Takes num_robots as a parameter (0, 1, or 2) - Returns the correct bonus: 0 points, 8 points, or 30 points

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Q30: Modify this function to have a default speed of 50:

def drive_forward(distance, speed):
    drivetrain.set_drive_velocity(speed, PERCENT)
    drivetrain.drive_for(FORWARD, distance, MM)

After modifying, what happens if you call drive_forward(500) without specifying speed?

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Section 3: Loops and Conditionals

Conceptual Questions (Q31-Q35)

Q31: What is a conditional statement? Give a real-world example and its Python equivalent.

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Q32: What is the difference between = and ==? Why is this a common mistake?

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Q33: When would you use while True: in robot code? Give a specific example.

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Q34: What is the difference between break and continue in a loop?

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Q35: In the driver control loop, we use wait(20, MSEC). Why is this necessary? What would happen without it?

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Code Reading Questions (Q36-Q40)

Q36: What does this code print?

score = 45

if score > 50:
    print("Great!")
elif score > 30:
    print("Good")
else:
    print("Keep trying")

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Q37: How many times does this loop run, and what does it print?

for i in range(3):
    print("Block " + str(i + 1))

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Q38: This code has a serious bug. What is it, and what will happen?

count = 0
while count < 5:
    print(count)

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Q39: What does this code output?

x = 10
if x > 5 and x < 15:
    print("In range")
else:
    print("Out of range")

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Q40: Trace through this code. What numbers are printed?

for i in range(5):
    if i == 3:
        break
    print(i)

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Push Back Application Questions (Q41-Q45)

Q41: Write an if-elif-else statement that checks your alliance's block count: - If 7 or more blocks: print "AWP Block Goal Met!" - If 4-6 blocks: print "Getting there!" - Otherwise: print "Need more blocks!"

Use blocks_scored = 8 to test.

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Q42: Write a while loop that: - Continuously reads the controller button A - If the button is pressed, prints "Button pressed!" and exits the loop - Waits 20 milliseconds between checks (use wait(20, MSEC))

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Q43: In Push Back driver control, write code that handles three button modes: - If R1 is pressed: multiply speed by 1.5 (turbo mode) - If L1 is pressed: multiply speed by 0.5 (precision mode) - Always clamp the result between -100 and 100

Start with speed = 80.

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Q44: Write a for loop that simulates scoring 5 blocks by: - Printing "Scoring block X" where X is the block number (1-5) - After the loop, print "Total blocks scored: 5"

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Q45: The Push Back autonomous period is 15 seconds. Write a simplified autonomous routine that: - Uses a while loop to check if time is remaining - Drives forward for each iteration - Stops when time runs out - Prints how many push attempts were made

# Start with these variables:
time_remaining = 15
push_attempts = 0
time_per_push = 3  # seconds per push attempt

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Answer Key

Section 1 Answers: Variables and Types

A1: A variable is like a labeled container that holds information. Think of labeled boxes in a kitchen: one labeled "SUGAR" holds sugar, one labeled "FLOUR" holds flour. In Python, speed = 50 creates a box labeled "speed" that holds the number 50. You can change what's inside the box, and you can use the label to get the contents.

A2: - = (single equals) is the assignment operator - it stores a value in a variable: speed = 50 - == (double equals) is the comparison operator - it checks if two values are equal: if speed == 50: - Common mistake: using = when you mean == in conditions!

A3: ALL_CAPS names (like WHEEL_TRAVEL_MM) follow Python convention for constants - values that shouldn't change during the program. They're not truly protected, but the naming tells other programmers "don't modify this value." These are typically configuration values like wheel measurements.

A4: Four basic data types: | Type | Example for Push Back Robot | |------|----------------------------| | int (integer) | team_number = 12345 or blocks_scored = 8 | | float (decimal) | wheel_diameter = 4.0 or gear_ratio = 2.5 | | str (string) | alliance = "red" or robot_name = "Push Bot" | | bool (boolean) | is_parked = True or has_zone_control = False |

A5: Step by step: 1. Initially: speed = 50 (speed holds 50) 2. Python evaluates the right side first: speed + 10 = 50 + 10 = 60 3. Then stores the result back in speed: speed = 60 4. Final value: 60

A6: Tracing through: 1. x = 10 → x is 10 2. x = x * 2 → x is 10 * 2 = 20 3. x = x - 5 → x is 20 - 5 = 15

Final value: 15

A7: - a = 42 → int (whole number) - b = 3.14 → float (decimal number) - c = "VEX" → str (text in quotes) - d = True → bool (boolean) - e = "100" → str (it's in quotes, so it's text, not a number!)

A8: Output:

Score: 15

Explanation: 5 * 3 = 15, then str(15) converts it to "15" for concatenation.

A9: The error: You can't add a string and an integer! - motor_port is "1" (a string) - You can't do "1" + 1

Fix:

motor_port = 1  # Make it an integer
actual_port = motor_port + 1  # Now works: 2

A10: The problem: Variable names can't contain hyphens (-) because Python thinks it's subtraction!

Fix: Use underscores instead:

my_robot_speed = 50

A11:

blocks_scored = 8
points_per_block = 3
total_score = blocks_scored * points_per_block
print("Alliance block score: " + str(total_score))
# Output: Alliance block score: 24

A12:

team_number = 12345          # int - whole number
robot_name = "Push Bot"      # str - text in quotes
is_parked = True             # bool - True or False
wheel_diameter = 4.0         # float - decimal number

A13:

field_feet = 12
mm_per_foot = 304.8
field_mm = field_feet * mm_per_foot

print("Field size: " + str(field_feet) + " feet")
print("Field size: " + str(field_mm) + " mm")
# Output:
# Field size: 12 feet
# Field size: 3657.6 mm

A14:

robots_parked = 2

if robots_parked == 2:
    parking_bonus = 30
elif robots_parked == 1:
    parking_bonus = 8
else:
    parking_bonus = 0

print("Parking bonus: " + str(parking_bonus))
# Output: Parking bonus: 30

A15: - WHEEL_TRAVEL_MM = 319.19 represents the distance traveled in one wheel rotation (circumference) in millimeters. This is for 4-inch omni wheels. - TRACK_WIDTH_MM = 295 is the distance between the left and right wheels. - ALL_CAPS because these are constants that shouldn't change during the program. - WHEEL_TRAVEL_MM is a float (has decimal). TRACK_WIDTH_MM is an int (but could be float).

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Section 2 Answers: Functions

A16: A function is like a recipe - a set of instructions with a name. Instead of writing all the steps every time you want to make a sandwich, you just say "make a sandwich." In Python, instead of writing 10 lines of motor control code everywhere, you define drive_forward() once and call it by name whenever needed.

A17: - Parameter: A variable in the function definition that receives a value. It's like a placeholder. - Argument: The actual value you pass when calling the function.

Example:

def greet(name):      # "name" is the PARAMETER
    print("Hello, " + name)

greet("Alice")        # "Alice" is the ARGUMENT

A18: return gives a result back to the code that called the function. - Without return: The function does its work but gives back None. You can't use the result. - With return: You get a usable value back.

# Without return
def add_no_return(a, b):
    result = a + b
    # forgot return!

x = add_no_return(5, 3)  # x is None!

# With return
def add_with_return(a, b):
    return a + b

y = add_with_return(5, 3)  # y is 8

A19: A default parameter has a preset value that's used if you don't provide one.

In def deadband(value, threshold=5.0):, the default for threshold is 5.0.

• deadband(50) uses threshold=5.0 (default)
• deadband(50, 10) uses threshold=10 (overridden)

A20: Benefits of putting code in a function: 1. Reusability: Call it from multiple places without copying code 2. Organization: Easier to understand what each part does 3. Maintainability: Fix bugs in one place, fixed everywhere 4. Testing: Can test the function independently 5. Readability: driver_control_loop() is clearer than 50 lines of code

A21: The function returns 20. - calculate_area(4, 5) passes width=4, height=5 - area = 4 * 5 = 20 - return area returns 20

A22: Two errors: 1. Missing colon after the function definition: should be def add_numbers(a, b): 2. Missing indentation on the body (though this might not show in the formatting)

Correct version:

def add_numbers(a, b):
    result = a + b
    return result

A23: Output:

Hello, Robot!
Hello, Team 12345!

- First call greet() uses default parameter "Robot" - Second call greet("Team 12345") uses the provided argument

A24: Tracing deadband(3, threshold=5): 1. value = 3, threshold = 5 2. Check: abs(3) < 5? → 3 < 5? → True 3. Since True, execute return 0.0 4. Returns 0.0

The joystick value 3 is below the threshold, so it's treated as zero (no drift).

A25: clamp(150, 0, 100) returns 100.

Breaking it down: 1. min(150, 100) = 100 (smaller of 150 and 100) 2. max(0, 100) = 100 (larger of 0 and 100) 3. Result: 100

The value 150 is clamped down to the maximum of 100.

A26:

def calculate_block_score(blocks):
    """
    Calculate total points from scored blocks in Push Back.

    Args:
        blocks: Number of blocks scored

    Returns:
        Total points (3 points per block)
    """
    points_per_block = 3
    return blocks * points_per_block

# Test:
print(calculate_block_score(8))  # Output: 24

A27:

def check_zone_control(our_blocks, opponent_blocks):
    """Check if our alliance controls a goal zone."""
    if our_blocks > opponent_blocks:
        return True
    else:
        return False
    # Or simply: return our_blocks > opponent_blocks

# Test:
print(check_zone_control(5, 3))  # True
print(check_zone_control(2, 4))  # False

A28: 1. Problem it solves: Joystick drift - even when you're not touching the controller, it might not read exactly 0. It might read 2 or -3.

1. Why important for block positioning: When you're carefully positioning blocks near a goal, tiny unwanted movements could push the block the wrong way or miss the goal. deadband ensures the robot stays still when you want it still.

2. Without deadband: The robot would constantly creep or drift even when you're not touching the joystick, making precise positioning nearly impossible.

A29:

def parking_bonus(num_robots):
    """Calculate parking bonus based on robots parked."""
    if num_robots == 2:
        return 30
    elif num_robots == 1:
        return 8
    else:
        return 0

# Test:
print(parking_bonus(0))  # 0
print(parking_bonus(1))  # 8
print(parking_bonus(2))  # 30

A30:

def drive_forward(distance, speed=50):  # Added =50 default
    drivetrain.set_drive_velocity(speed, PERCENT)
    drivetrain.drive_for(FORWARD, distance, MM)

# Now drive_forward(500) uses speed=50 automatically
# drive_forward(500, 75) would use speed=75

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Section 3 Answers: Loops and Conditionals

A31: A conditional statement lets code make decisions based on whether something is true or false.

Real-world: "If it's raining, take an umbrella. Otherwise, wear sunglasses."

Python:

if is_raining:
    take_umbrella()
else:
    wear_sunglasses()

A32: - = is assignment (store a value): speed = 50 - == is comparison (check equality): if speed == 50:

Common mistake: Writing if speed = 50: (syntax error!) instead of if speed == 50:

Memory trick: "Double equals to compare, single equals to declare."

A33: while True: creates an infinite loop that runs forever (until you break or the robot turns off).

Use in robot code: The driver control loop

while True:
    # Read joysticks
    # Control motors
    wait(20, MSEC)

This runs continuously during the driver control period, constantly updating motor speeds based on joystick position.

A34: - break: Exits the entire loop immediately - continue: Skips the rest of this iteration and goes to the next one

for i in range(5):
    if i == 2:
        break      # Stops at 2, prints: 0, 1
        # continue  # Skips 2, prints: 0, 1, 3, 4
    print(i)

A35: wait(20, MSEC) pauses for 20 milliseconds (0.02 seconds).

Why necessary: 1. Without it, the loop runs millions of times per second 2. Uses excessive CPU power 3. Can cause the V5 Brain to overheat or lag 4. 20ms = 50 updates per second, which is smooth enough for control

Without it: The brain would be overwhelmed, controls would be sluggish, and the robot might become unresponsive.

A36: Output: "Good"

Tracing: 1. score = 45 2. Is 45 > 50? No → skip "Great!" 3. Is 45 > 30? Yes → print "Good" and stop checking

A37: The loop runs 3 times and prints:

Block 1
Block 2
Block 3

range(3) produces 0, 1, 2. We add 1 to each for display.

A38: Infinite loop! The code will run forever because count never changes.

The loop checks count < 5 (0 < 5 = True), prints 0, then checks again... forever printing 0.

Fix: Add count = count + 1 inside the loop:

count = 0
while count < 5:
    print(count)
    count = count + 1  # This was missing!

A39: Output: "In range"

Tracing: - x = 10 - Is x > 5? → 10 > 5 → True - Is x < 15? → 10 < 15 → True - True and True → True → print "In range"

A40: Output:

0
1
2

Tracing: - i=0: Is 0==3? No → print 0 - i=1: Is 1==3? No → print 1 - i=2: Is 2==3? No → print 2 - i=3: Is 3==3? Yes → break (exit loop immediately)

3 and 4 are never printed because break exits before printing.

A41:

blocks_scored = 8

if blocks_scored >= 7:
    print("AWP Block Goal Met!")
elif blocks_scored >= 4:
    print("Getting there!")
else:
    print("Need more blocks!")

# Output: AWP Block Goal Met!

A42:

while True:
    if controller.buttonA.pressing():
        print("Button pressed!")
        break
    wait(20, MSEC)

A43:

speed = 80

if controller.buttonR1.pressing():
    speed = speed * 1.5  # Turbo: 80 * 1.5 = 120
elif controller.buttonL1.pressing():
    speed = speed * 0.5  # Precision: 80 * 0.5 = 40

# Clamp to valid range
speed = clamp(speed, -100, 100)

# If R1 was pressed: speed is now 100 (clamped from 120)
# If L1 was pressed: speed is now 40
# If neither: speed stays 80

A44:

for block_number in range(1, 6):  # 1, 2, 3, 4, 5
    print("Scoring block " + str(block_number))

print("Total blocks scored: 5")

Output:

Scoring block 1
Scoring block 2
Scoring block 3
Scoring block 4
Scoring block 5
Total blocks scored: 5

A45:

time_remaining = 15
push_attempts = 0
time_per_push = 3

while time_remaining > 0:
    # Simulate pushing
    print("Push attempt " + str(push_attempts + 1))
    # drivetrain.drive_for(FORWARD, 500, MM)  # In real code

    push_attempts = push_attempts + 1
    time_remaining = time_remaining - time_per_push

print("Autonomous complete!")
print("Total push attempts: " + str(push_attempts))

Output:

Push attempt 1
Push attempt 2
Push attempt 3
Push attempt 4
Push attempt 5
Autonomous complete!
Total push attempts: 5

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Score Tracker

Section	Your Score	Out Of
Variables and Types	___	15
Functions	___	15
Loops and Conditionals	___	15
TOTAL	___	45

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